EDIT

copied from #6049 :

Remembering the old filters works well even when changing the datasource or reopening the editor.

Not yet fully correct IMO is that the filter works almost the same for all attributes but should be independent.
E.g. the geographic scope of a classification might want to have a different filter cache as the distribution areas and again a different one than specimen areas.

Currently to me it seems that only the specimen areas do have a special rule which always includes countries. IMO for specimen only the starting filter should be different (including only countries) for all others by default all areas should be shown.
But for each attribute we should have our own filter cache stored.