It's possible that there was a change made to the JSON bookmark format between the versions since they are so far apart.

Other than the obvious exporting using HTML instead (as you've already mentioned), perhaps you could try loading your Firefox 68 profile with Firefox 54 instead and then importing the bookmarks. Hypothetically, Firefox should be able to open the bookmarks in that case.

In reality, you shouldn't still be using Firefox 54 if you are on a system that can updated to the most recent versions. There are a lot of critical security bugs that you are vulnerable to if you are running the older version of Firefox.

Your chances of success might be higher if you replace places.sqlite instead of trying to restore a JSON backup.

You can check for problems with the places.sqlite and favicons.sqlite files in the Firefox profile folder.

• use "Verify Integrity" button on the "Help -> Troubleshooting Information" (about:support) page

In case errors are reported with "Verify Integrity" close and restart Firefox and retry.

I tried the Verify Integrity. It didn't help.

I'm reluctant to open Firefox 68 with the Firefox 54 profile because I've done considerable customization already of Firefox 68 & don't want to screw things up - or screw up Firefox 54 which I may still depend on while trying to make Firefox 68 work as I want it to.

So, I've bit the bullet and started to hand modify the 68 bookmarks.

Aside: I've been using Firefox since Version 1 (& have used IE & Chrome). I've never understood why it isn't possible in any browser to export/import a selection of bookmarks.

RemySecor said

Aside: I've been using Firefox since Version 1 (& have used IE & Chrome). I've never understood why it isn't possible in any browser to export/import a selection of bookmarks.

I'm not sure how this would work between versions, but have you tried simply selecting and copying the bookmarks from one version and then pasting them into the other version of Firefox? I know it works on the same version, but as I said I'm not sure how well it works with a different version.

While it would actually likely be a really useful feature, Firefox doesn't currently allow you to export only specific bookmarks. The closest option for that would be to export your bookmarks to an HTML file and then use a text editor to remove the ones you don't want. That would require a basic knowledge of the HTML format, but it's not impossible for a regular user.

Copying and pasting bookmarks via the clipboard from one Firefox version (profile) to another Firefox instance only works for bookmarks and not for folders. If you copy a folder then you only get the folder ID (GUID) on the clipboard and not the content of the folder, so a copy/paste of a folder only works in the the same Firefox instance.

You can still try the Firefox 54 places.sqlite in a new Firefox 68 profile and possibly export the bookmarks to JSON if this works.

cor-el said

Copying and pasting bookmarks via the clipboard from one Firefox version (profile) to another Firefox instance only works for bookmarks and not for folders.
If you copy a folder then you only get the folder ID (GUID) on the clipboard and not the content of the folder, so a copy/paste of a folder only works in the the same Firefox instance.

While that is true, a simple workaround would be to simply copy the contents of each folder separately and then manually create the folder on the other version to paste that in to.