When I create a new item, I can add it to item sets.
In the pane for adding it to item sets, I have an instant search to find more quickly an exact item set.
In Omeka S 3, if I start to type the name of an “item set” until that specific item set is the only one I see in the list, and click on it to add it, I get the following message in the item set pane:
All item sets have been added.
See screenshot (notice also that the text appears in English even if Omeka S is set in another language)
The item set is added, but if I want to add others, I have to save, and edit the item again… only then I see again all item sets.
I am quite sure I did not have this isssue with Omeka S 2.x.