I can’t remember when I first started using BookMacster. I have pruned my old dead bookmarks, synchronized multiple browsers on multiple boxes, and sometimes did some re-arrangement of bookmarks. It has never failed to do what I asked (even if I asked for the wrong thing). It works both via direct network access and by sharing the saved .bmco file. I have used the saved .bmco file to recover from unwanted results when merging a new user Safari instance into iCloud syncing - which happens by merging whatever bookmarks exist by default with what is already synced by iCloud.
My strategy is to designate my desktop Safari instance as the master and to use BookMacster to save and distribute the bookmark set to other browsers such as Firefox. Having a local .bmco file makes backup and restore of bookmarks a completely local function, not at the mercy of any cloud subscription.