Suddenly I realized that this is exactly what is missing after switching from ff to chrome, clicked the menu - I did not find anything like it, but I wasn’t upset, but I typed in “chrome favorites bar separator” in Google and found the very first link, started a long time ago ... And in it there were worthy people who immediately came up with and implemented the solutions on their own!
1.
scoobo.com/separator - in fact, the separator itself. Crutch, of course, but it works.

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2.
separatethis.com - the horizontal separator inside the folder may also be useful.
Try, if you are on chrome, suddenly this is what you need.