just a quick fwiw before i try to reply to the longer message by max. my own suggestion is modest for metadata, [even for science papers and things with funny web construction]. just title like org-capture extension. no need to cite in my case.
my needs for saving and restoring, however, are more fancy. something like achieving a 1:1 mapping from firefox selected tabs, or a tree style tabs extension tree, to their counterparts in org, even when those counterparts have notes and such. this might include marking the org version as deleted/doneified] merely by closing tab in firefox. vice-versa would be straightforward. so it's really a "get organized and don't get confused by having both firefox and org" kinda thing.