jAlbum 19.0.6 is now available as a core update. It fixes the following issue:
Folder tree wouldn't sometimes update on newly added or deleted sub folders (happens when navigating to a folder via the Explorer thumbnails)
This bug appeared in v19 in an attempt to fix another folder tree related issue (In v19, I reverted to older code that resulted in this bug instead). With the 19.0.6 update I now believe the folder tree behavior is solid, but please report if it behaves for you too before I add it to the official archives.