[ENH] Improve managment of multivalued attributes

When changing values on a multivalued attribute, interface looks like this :

which let add or remove values, but not update current values.
Current values should be directly updated without remove/readd

Start by locating the frontend interface for editing multivalued attributes and inspect the existing add/remove flow shown in the issue. Determine how current values are represented and edited. Done means existing values can be changed directly without removing and re-adding them.

Written by the indexing model from the issue text.