The list of grammatical features should look similar as outline in the hand-drawn mock shown in T162790.
In order to achieve, check there is an existing UI widget that could be used to create such a list. To my best knowledge, there is no such list in Wikibase UI so far, so we cannot just something we already have.

After brainstorming with @Aleksey_WMDE and @Jakob_WMDE we concluded that:

• We're not sure if the palette of jquery ui widget Wikibase widely uses has something similar. Should it had, it would be a way to go.
• There seems to be such widgets in OOUI. E.g. CapsuleMultiselectWidget (see https://doc.wikimedia.org/oojs-ui/master/demos/) looks to me like a good possible candidate.

The purpose of this task is to verify if there is a widget that fits the needs of the parent task. I.e. it should provide needed adding/removing item to the list functionalities. Furthermore, it should be possible to plug item lookup into it somehow, as the intended

If the conclusion of this investigation is that there is no existing widget we could use, we need to decide on alternatives. E.g. are we going to create the widget we need ourselves (would it then be jquery ui widget or OOUI one, or something completely different?), or do we decide to have some other way of editing the list of grammatical features than the one depicted in T162790.