Hi @NaoDesu! Unfortunately it seems that I wasn't able to shoot out every bug before release... I will try to fix it as fast as I can, but I need to be able to reproduce the bug on my end. If you could add more information about your Firefox version and OS, that would be awesome! Anyways, thanks for trying Tabby out.

Hi! Have you tried editing the settings? If you go into Add-ons, and click on the three dots beside Tabby and click on Preferences, it will open the settings page where you can set the scale of everything in the popup, and the size of the popup window itself. (the settings page is quite hidden right now, so I will fix that in the future release)

Edit: Tabby actually has a standalone settings page, which is why it isn't in one of the tabs. I created this guide with images on how to access the settings page. I do admit that it is hard to describe in words how to access the page. I hope this helps! https://github.com/Bill13579/tabby/wiki/How-to-Access-the-Settings-Page

The reason that the height is limited to 600px, is that Firefox limits the size of popups to 800x600px, so unfortunately, it is a limit imposed by the browser which I cannot work around. Sorry if the popup is small though; if I could increase the limit, I would do that right now.