To open the Bookmarks Manager, press the Alt or F10 key bring up the tool bar, and select Bookmarks. Hot key is <Control>(Mac=<Command>) <Shift> B.

Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Export Bookmarks To HTML, and follow the prompts and save it to a HTML file. Copy the file to another computer. Repeat the instructions above, BUT select Import Bookmarks From HTML,

Thanks, FredMcD. I had already tried your suggestion but it's a pain, at least in my hands/system: the HTML file is imported, yes, but Safari crashes the moment I start relocating bookmarks or folders. This is one of the reasons I keep using FF, Safari is ridiculously unstable and the bookmarks management is particularly so -not to mention the features it lacks. Anyway, I'm still hoping someone can say if the direct import fails because of FF or Safari. Of course, none of this would matter if I could work with FF in iOS. I tried it a while ago and, sadly, I found syncing between desktop and iPad was no better than with Safari. Maybe I should try again.

Have you checked with Safari support? How many bookmarks do you have?

Impossible to reach Safari support. I get into a weird loop that seems to let me ask about anything but Safari. The manual, of course is useless: it describes things as they "should" be and my particular issue isn't contemplated. In one of the communities, I found I'm not alone (https://discussions.apple.com/thread/7630704?start=0&tstart=0) but that's it; the last entry of the thread suggests asking in Mozilla support.

How many bookmarks...? Don't know. My guess is around "an awful lot" but I have many (nested) folders. In case it helps, the size of the JSON file is 12.2 MB and the HTML file is 16,6 MB.

I called for more help.