Hello Stan, yes this is one of the benefits of BSP2 to go past FF corruptions in the native bookmarks DB when they appear / already exist.

A careful way to proceed, but which loses tags if you have any (until FF allows us to copy tags :-( ) is typically:
- Go in BSP2 to a folder which is not showing anymore in the native sidebar
- Copy it (right click and click "Copy")
- Go to another place which is not corrupt
- Right click there and click "Paste before" or "Paste into" if a folder
- Go to the native sidebar, and verify the copied folder is there
- When all is good (can take some time when folders are big), you can delete the old "lost" folder in BSP2

A bolder way to proceed, but which should keep the tags, is typically:
- Go in BSP2 to a folder which is not showing anymore in the native sidebar
- Cut it (right click and click "Cut") - you are safe so far, as Cut does not remove anything, it just says that a future paste will be a move instead of a copy
- Go to another place which is not corrupt
- Right click there and click "Paste before" or "Paste into" if a folder - this step is safe in fact, except when FF crashes or the corruption is too strong .. should be very rare though
- Go to the native sidebar, and verify the moved folder is there

Hope this helps. If any problem, let me know on https://github.com/aaFn/Bookmark-search-plus-2/issues

Note that FF corrupts its bookmark DB on its own .. BSP2 does not play a role in that.
This is why there is a backup function of bookmarks in FF (saved everyday automatically by FF, you can find the backups in one of the menus of the Bookmarks Library).