After install on my Firefox based Mullvad browser and being automatically set as default 'New tabs' Browser's Home Settings, it worked right away when using the 'Open a new tab' (+/plus sign tab button) without a 'Pin to Toolbar' option needed nor seems to be supported.

Pros and like(s):
1. The full browser screen display
2. Plenty enough useful GUI/Display settings
3. Wallpaper feature and custom image option
4. Shortcuts feature and its options (even move their position by way of drag and drop)
5. Data Backup feature (Export and Import)

Cons and don't like(s): From the Wallpaper feature I haven't got the Upload "custom" Image working yet (repeatedly error message about file size). Otherwise than that, nothing but if anything else, yet to be discoverd.