diff --git a/addons/web_editor/static/src/js/editor/snippets.editor.js b/addons/web_editor/static/src/js/editor/snippets.editor.js
index b56b16bb044..8d6a3857218 100644
--- a/addons/web_editor/static/src/js/editor/snippets.editor.js
+++ b/addons/web_editor/static/src/js/editor/snippets.editor.js
@@ -693,6 +693,8 @@ var SnippetEditor = Widget.extend({
         this.styles = {};
         this.selectorSiblings = [];
         this.selectorChildren = [];
+        this.selectorLockWithin = new Set();
+        const selectorExcludeAncestor = new Set();
 
         var $element = this.$target.parent();
         while ($element.length) {
@@ -740,6 +742,12 @@ var SnippetEditor = Widget.extend({
             if (val['drop-in']) {
                 this.selectorChildren.push(val['drop-in']);
             }
+            if (val['drop-lock-within']) {
+                this.selectorLockWithin.add(val['drop-lock-within']);
+            }
+            if (val['drop-exclude-ancestor']) {
+                selectorExcludeAncestor.add(val['drop-exclude-ancestor']);
+            }
 
             var optionName = val.option;
             var option = new (options.registry[optionName] || options.Class)(
@@ -774,6 +782,13 @@ var SnippetEditor = Widget.extend({
             return option.appendTo(document.createDocumentFragment());
         });
 
+        if (selectorExcludeAncestor.size) {
+            // Prevents dropping an element into another one.
+            // (E.g. ToC inside another ToC)
+            const excludedAncestorSelector = [...selectorExcludeAncestor].join(", ");
+            this.excludeAncestors = (i, el) => !el.closest(excludedAncestorSelector);
+        }
+
         this.isTargetMovable = (this.selectorSiblings.length > 0 || this.selectorChildren.length > 0);
 
         this.$el.find('[data-bs-toggle="dropdown"]').dropdown();
@@ -1006,40 +1021,34 @@ var SnippetEditor = Widget.extend({
             width: self.$target.width(),
             height: self.$target.height()
         };
-        const closestFormEl = this.$target[0].closest('form');
-        self.$target.after('<div class="oe_drop_clone" style="display: none;"/>');
+        const dropCloneEl = document.createElement("div");
+        dropCloneEl.classList.add("oe_drop_clone");
+        dropCloneEl.style.setProperty("display", "none");
+        self.$target[0].after(dropCloneEl);
         self.$target.detach();
         self.$el.addClass('d-none');
 
         var $selectorSiblings;
         for (var i = 0; i < self.selectorSiblings.length; i++) {
-            if (!$selectorSiblings) {
-                $selectorSiblings = self.selectorSiblings[i].all();
-            } else {
-                $selectorSiblings = $selectorSiblings.add(self.selectorSiblings[i].all());
+            let $siblings = self.selectorSiblings[i].all();
+            if (this.excludeAncestors) {
+                $siblings = $siblings.filter(this.excludeAncestors);
             }
+            $selectorSiblings = $selectorSiblings ? $selectorSiblings.add($siblings) : $siblings;
         }
         var $selectorChildren;
         for (i = 0; i < self.selectorChildren.length; i++) {
-            if (!$selectorChildren) {
-                $selectorChildren = self.selectorChildren[i].all();
-            } else {
-                $selectorChildren = $selectorChildren.add(self.selectorChildren[i].all());
+            let $children = self.selectorChildren[i].all();
+            if (this.excludeAncestors) {
+                $children = $children.filter(this.excludeAncestors);
             }
+            $selectorChildren = $selectorChildren ? $selectorChildren.add($children) : $children;
         }
-        // TODO In master, do not reference other module class + find a better
-        // system to define such cases + avoid duplicated code (drag & drop from
-        // editor panel + drag & drop from move button of existing block).
-        // Prevent dropping ToC inside another ToC. grep: NO_DOUBLE_TOC
-        if (this.$target[0].classList.contains('s_table_of_content')) {
-            $selectorChildren = $selectorChildren.filter((i, el) => !el.closest('.s_table_of_content'));
-        }
-        // Disallow dropping form fields outside of their form.
-        // TODO this can probably be implemented by reviewing data-drop-near
-        // definitions in master but we should find a better to define those and
-        // such cases.
-        if (this.$target[0].classList.contains('s_website_form_field')) {
-            const filterFunc = (i, el) => el.closest('form') === closestFormEl;
+        // Disallow dropping an element outside a given direct or
+        // indirect parent. (E.g. form field must remain within its own form)
+        for (const lockedParentSelector of this.selectorLockWithin) {
+            const closestLockedParentEl = dropCloneEl.closest(lockedParentSelector);
+            const filterFunc = (i, el) => el.closest(lockedParentSelector) === closestLockedParentEl;
             if ($selectorSiblings) {
                 $selectorSiblings = $selectorSiblings.filter(filterFunc);
             }
@@ -2868,6 +2877,8 @@ var SnippetsMenu = Widget.extend({
                 '$el': $style,
                 'drop-near': $style.data('drop-near') && self._computeSelectorFunctions($style.data('drop-near'), '', false, noCheck, true, excludeParent),
                 'drop-in': $style.data('drop-in') && self._computeSelectorFunctions($style.data('drop-in'), '', false, noCheck),
+                'drop-exclude-ancestor': this.dataset.dropExcludeAncestor,
+                'drop-lock-within': this.dataset.dropLockWithin,
                 'data': Object.assign({string: $style.attr('string')}, $style.data()),
             };
             self.templateOptions.push(option);
@@ -3241,6 +3252,7 @@ var SnippetsMenu = Widget.extend({
                     var $baseBody = $snippet.find('.oe_snippet_body');
                     var $selectorSiblings = $();
                     var $selectorChildren = $();
+                    const selectorExcludeAncestor = [];
                     var temp = self.templateOptions;
                     for (var k in temp) {
                         if ($baseBody.is(temp[k].base_selector) && !$baseBody.is(temp[k].base_exclude)) {
@@ -3250,17 +3262,17 @@ var SnippetsMenu = Widget.extend({
                             if (temp[k]['drop-in']) {
                                 $selectorChildren = $selectorChildren.add(temp[k]['drop-in'].all());
                             }
+                            if (temp[k]['drop-exclude-ancestor']) {
+                                selectorExcludeAncestor.push(temp[k]['drop-exclude-ancestor']);
+                            }
                         }
                     }
 
-                    // TODO In master, do not reference other module class +
-                    // find a better system to define such cases + avoid
-                    // duplicated code (drag & drop from editor panel + drag &
-                    // drop from move button of existing block).
-                    // Prevent dropping ToC inside another ToC.
-                    // grep: NO_DOUBLE_TOC
-                    if ($baseBody[0].classList.contains('s_table_of_content')) {
-                        $selectorChildren = $selectorChildren.filter((i, el) => !el.closest('.s_table_of_content'));
+                    // Prevent dropping an element into another one.
+                    // (E.g. ToC inside another ToC)
+                    for (const excludedAncestorSelector of selectorExcludeAncestor) {
+                        $selectorSiblings = $selectorSiblings.filter((i, el) => !el.closest(excludedAncestorSelector));
+                        $selectorChildren = $selectorChildren.filter((i, el) => !el.closest(excludedAncestorSelector));
                     }
 
                     $toInsert = $baseBody.clone();
diff --git a/addons/website/views/snippets/s_table_of_content.xml b/addons/website/views/snippets/s_table_of_content.xml
index c233d978d0b..8a3b207329c 100644
--- a/addons/website/views/snippets/s_table_of_content.xml
+++ b/addons/website/views/snippets/s_table_of_content.xml
@@ -57,7 +57,7 @@
         </div>
     </xpath>
     <xpath expr="." position="inside">
-        <div data-js="TableOfContent" data-selector=".s_table_of_content"/>
+        <div data-js="TableOfContent" data-selector=".s_table_of_content" data-drop-exclude-ancestor=".s_table_of_content"/>
         <div data-js="TableOfContentNavbar" data-selector=".s_table_of_content_navbar_wrap">
             <we-button-group string="Position">
                 <we-button class="fa fa-fw fa-long-arrow-left" title="Left" data-navbar-position="left"/>
diff --git a/addons/website/views/snippets/s_website_form.xml b/addons/website/views/snippets/s_website_form.xml
index 90dce371183..1e6120b99a1 100644
--- a/addons/website/views/snippets/s_website_form.xml
+++ b/addons/website/views/snippets/s_website_form.xml
@@ -74,7 +74,8 @@
         </div>
 
         <div data-js='WebsiteFieldEditor' data-selector=".s_website_form_field"
-             data-exclude=".s_website_form_dnone" data-drop-near=".s_website_form_field">
+             data-exclude=".s_website_form_dnone" data-drop-near=".s_website_form_field"
+             data-drop-lock-within="form">
             <we-select data-name="type_opt" string="Type" data-no-preview="true">
                 <we-title>Custom field</we-title>
                 <we-button data-custom-field="char">Text</we-button>