One of the primary feedback that we received after deploying T298960: Create the message group/prefix selector component was that: without any search text, no groups are displayed.

Expected behavior is that all the groups would be shown. We had considered this earlier but decided against doing it primarily due to performance reasons.

When the entity selector is configured to fetch only message prefixes or groups, we could add pagination. This would help to implement the expected behavior mentioned in the feedback.

So if the user enters "G", then we will fetch 10 groups that contain "G", and as the user scrolls down, we'll fetch the next 10 and so on. The pagination is needed to ensure that the performance does not suffer due to use fetching all the groups/message prefixes at once.

Some time will need to be spent reviewing whether something like this is feasible with OOUI.