Hello Oshoreiki,
Please contact me to my support email with additional info (what exactly is not working as expected).
I haven't made any changes for last 4 months, so things should work as before (I'm testing it with every new Beta / Nightly release).
Also there will be a new version 14.0 released any day now so if you found some bugs, please let me know and I can include the fix in the new version.

Best regards,
Juraj Mäsiar

Hello,
I've just tried it with my Nightly and I can confirm this strange auto-closing tab behavior.
However this 99.9% not caused by my addon. There is no code for handling addressbar actions (not even permission), so this must be some Firefox bug.

I tired to reset my profile for Firefox Nightly using Reset button in the about:support page only to find out, the button doesn't work :). Yet another bug... Luckily reset button on the official support page works:
https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings
Resetting profile fixed the problem in my case (make sure to user Firefox Sync. to backup list of installed addons and make sure to backup any addons data, because these are not backed up! So export your dials first).

Lastly I would like to mention that Nightly is NOT recommended for daily usage and should be used ONLY for testing. You should stick with Release version or Beta (Developer Edition), which contains much less bugs, but sometimes some serious appears as well.

If you have more questions, feel free to contact me to my support email.

Best regards,
Juraj Mäsiar

Hello,
Cloud sync for settings will come, I already started working on it but it got a bit complicated so I had to stop it for now. I want to make it flexible, allow users to share same settings across all devices or just backup each device setting separately.

Regarding your second request, this may be possible, but I will need a bit more info. Could you please contact me to my support email?

Best regards,
Juraj Mäsiar

Hello,
The issues with thumbnails generation should be fixed in the upcoming version 14.0.
Regarding dark-mode - you mean you use some other addon for making pages look dark and you want to use it for thumbnails as well, right? The Refresh by visiting page should work fine (right?), also there will be a new refresh method that should work as well (I will add some switch to the options page to change default thumbnails generation method).

Feel free to contact me to my support e-mail to discuss this further.

Also I'm really busy with a new release so I'm replying very fast these days...

Best regards,
Juraj Mäsiar

Hello,
Yes, I'm really sorry but this is very hard to do... I have no idea how to implement it right and there is so many other features that needs to be done.
Until then, you can do this on desktop and let changes synchronize over the cloud.
Best regards,
Juraj Mäsiar

Hello,

I haven't released new version for a long time now so this is most probably related to something in your Firefox profile (since so far nobody else is reporting this).
You can try to reinstall my add-on (make sure to export your dials to a file first), but it that won't help, I would suggest you to use Firefox Reset - this often fixes many profile-related bugs:
https://support.mozilla.org/kb/refresh-firefox-reset-add-ons-and-settings
Resetting profile will preserve your passwords, bookmarks and other important things (but not add-ons data).
Before resetting your profile I would suggest you to setup Firefox Sync. - this will backup the list of installed add-ons and after reset it will reinstall them.

Feel free to contact me to my support e-mail if it didn't help (of if it helps).

Best regards,
Juraj Mäsiar