This could (should?) be considered a refactoring, but this is actually
trying to restore lost functionality. In v10, the custom form widgets
were created with access to the node element that define them. We lost
that in v11, with the new views.
However, it is actually very useful for generic widgets. Since this is
not really a risky fix, I think that it can be done in 11.0.
Note: this feature was already reintroduced in master in commit
https://github.com/odoo/odoo/commit/b7aa439826df6b3e442b3f60bb593ff28efc8679
Géry Debongnie
c7b5b12be6