It works, but it doesn't preserve the history's "Most Recent Visit" dates, and all history items are loaded in sequentially in reverse order.
Still, for what I needed it to do, it worked. I have a couple of questions for the developer, however:

1. I know this add-on was intended to be "quick and dirty", but do you intend to continue working on it at all? This is the very first add-on I've ever used that *finally* delivered what I've been searching *years* for! So, I'd love for it to achieve its full potential with one or two more features.

2. If you are not planning on further development, would you be able to direct me to a similar add-on that *does* preserve history items' dates/times?

Thank you for your time and effort, Skyweb. I nearly gave up on the idea of being able to save my FireFox history. I look forward to your reply.

Export functionality:
The export seems to work. After installation, go to Manage add-ons. There you can export and import the history. When exporting, I receive a file "data.json". I have not tested whether this is error-free or complete. But it seems to be. For me, this is already worth 5 stars, because you can finally save the history in plain text.

Import functionality:
What did not work on my computer (Firefox 114.0.1, 64-bit, Windows, German) is the import. A file can be selected for import, but with the just exported file "data.json" in the size of 669 kByte only the name was displayed in the add-on, an actual import did not take place here. After selecting and confirming the file, nothing happened. I hope the programmer can change this in a future version.

Data protection:
The code is only a few lines and in the current version no data is transferred from your own computer to the outside at any time, everything is done locally. TOP!

Thank you for this already useful add-on!