A Form has a list of grammatical features to indicate the tense, case and similar features of a form. T162788 creates a basic non-editable view of these grammatical features. We now want to have them be editable as well. Each feature should be a link to an existing Wikidata item.
whiteboard mockup by @thiemowmde:
* I can edit existing grammatical features.
* Saving them is persisted through a page reload.
* I can only select existing items as grammatical features.