ok i see... there's indeed a link that opens full Bookmarks view at the bottom of the panel... i didn't noticed it as I only checked the 3-dot menu at the top.
however, it still don't see any way to select multiple bookmarks in the full view in the following way:
select the first desired bookmark > hold shift > select the last desired bookmark to select at once all bookmarks between the first and last selection (just like you select files in the Finder or bookmarks in other browsers).
you'll need to select each bookmark separately to add them to the selection of multiple bookmarks.
or am I missing something?