Yes, Roaming. The Local one has temporary files you can do without.

In the main profile folder where you found logins.json/key4.db, you will also find the session history files that store your open tabs.

When Firefox is closed:

Look for a sessionstore.jsonlz4 file at the main level of the profile folder. This usually is in good shape because it is created during a normal shutdown. When transferring, the "receiving" Firefox needs to also be done shutting down.

When Firefox is open:

It is updating files in the sessionstore-backups subfolder. You can back these up, but the other file is preferred.

Ref: Profiles - Where Firefox stores your bookmarks, passwords and other user data

Thinking I may need to use about:profiles and select new one. Not sure what will happen, hope it lets me point to new file on my USB drive.

No, I suggest that you never tell Firefox to directly access removable media (using any kind of Browse/Open button). This can cause unpredictable problems where it locks up for a minute waiting for the system to time out searching for the removable media when it isn't present. If you want to do a whole folder transplant, see:

https://support.mozilla.org/en-US/questions/1474421#answer-1687884

Note: your "Source" in step (1) can be the USB drive.

Here is what I did first before this post and I am pretty happy with it, but I had to try something else!

I moved from my roaming file bookmarks.html, key4.db, logins.json, folder Bookmarks, bookmarks.htlm and I think favicons.sqlite. All was well, I just didn't have a few things like my normal startup tabs which was no big deal. Had all my bookmarks and passwords. I was happy.

But sometimes I can't leave well enough alone. Thought I would try something that ended up driving the computer nuts, CPU 100 until I killed FF. I copied my roaming over on the new computer. Then I renamed by adding OLD. in front of new computer's profile. Then I renamed the profile I copied over from my roaming profile to the name that was on new computer originally. Started FF and I get get it to open all my default tabs, but it was just going nuts on CPU and beating the disk. I thought for sure this would work- but no.

So I killed FF and put it back to where I had just moved roaming file bookmarks.html, key4.db, logins.json, folder Bookmarks, bookmarks.htlm and I think favicons.sqlite. That seems good enough, got my passwords and bookmarks.

By default, Firefox doesn't use bookmarks.html, although you can export bookmarks in that format. Probably you also moved places.sqlite (bookmarks + history).

Yes it looks like I did copy over places.sqlite you mentioned.

I think these are the main ones, I can reload the add on like noscripts etc. Copying these seem to get most of what I wanted done on my testing. I don't know why copying over my main computer profiles onto backup computer and renaming them to what the name already was on backup computer didn't work. Caused problems. Anyway ordering new computer Monday so been testing this out so FF works at least for passwords and bookmarks on new machine.

I know I can also do an export of passwords within FF, never have tried that, seems I should be able to export then import to new computer, but this seems to get same things dome and get bookmarks.

What I copied from my Roaming Profile is below.

Q:\Firefox\bookmarks-2025-09-10.json Q:\Firefox\favicons.sqlite Q:\Firefox\key4.db Q:\Firefox\logins.json Q:\Firefox\Bookmark Q:\Firefox\bookmarks.html

Under Q:\Firefox\Bookmark" Folder are these 3 files Q:\Firefox\Bookmark\favicons.sqlite Q:\Firefox\Bookmark\places.sqlite Q:\Firefox\Bookmark\bookmarkbackups

Under Bookmarkbackups Folder were these, don't know but assume FF keep some backups, doesn't seem to be any sequence to the dates? They did all show the same create date of 9/10/25 with modified date same as date in the file name which is a modified date prior to create date. Oh I know, it was on the 9/10/2025 that I copied to mu USB.

Q\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-07-30_934_q6mrp0DTDyJCe2wKvZ_TjY7bHlzUBlLDCghnJY67j_g=.jsonlz4 Q:\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-02_935_dKWV99UmBP3LPOm4ghCxwD-hq5JL9KXv_ML3nCXk6u8=.jsonlz4 Q:Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-06_940_FmOAZPHnIOCUIRy8s8AAJh0RVsU8UHhAHjDtMe50XmY=.jsonlz4 Q:\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-07_940_-l0dTV305A6EtFIoyzxXfuZNuYQPTwtiVsKS5LtlQWo=.jsonlz4 Q:Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-13_941_xWZ9RVqvLTdx3vMyHAD53EUu756CFwi63rtADYOjYCk=.jsonlz4 Q:Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-14_942_KJPJJA705dDA-2TUDtfzKvqjWMmTAVeXETDlOXcPU9Y=.jsonlz4 Q:\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-18_943_ZDUbQtPx-XQo7uwLslfDPEi6VBFnfjbeqFKT4F6bqqY=.jsonlz4 Q:Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-20_946_9A8MM79_3klAI5zeX4HOmtZXFd0u9YCS2Zf-qZ3CKwc=.jsonlz4 Q:Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-22_947_RKWkd0h5qpVbg8mNjiTN0xEIrzmRxUgKu_jv1DzQkBI=.jsonlz4 Q:Firefox\Bookmark\bookmarkbackups\bookmarks-2025-08-26_949_k3WVKbAPzxIo40cYPeJhQ0KutuBMOxY7pDhDksj566E=.jsonlz4 Q\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-09-07_947_tiFcLTV9szwIMjLHVcclOZDqMpIBHkPPBmkJlSX7qag=.jsonlz4 Q\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-09-09_948_AlNJfs_af0r6vIBOVAWgxPmm9fuD0FPp1_oPnCj7Xjc=.jsonlz4 Q:\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-09-10_949_9SNhreGdW-ARq6K0uHyuZL5-vi6RbvO60vbS5FQLnoY=.jsonlz4 Q\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-07-28_931_SFe9XrmNRWBP8qEbuLionedoKyGuMM5ZGbvWroLdwKU=.jsonlz4 Q\Firefox\Bookmark\bookmarkbackups\bookmarks-2025-07-29_933_EZ9iBId33PvLAztBmCo_4tsIR_MMIbI5CRyX8GiHSuw=.jsonlz4