Move tabs to the side button is barely visible

[sy-be]

"Move tabs to the side" button is barely visible on dark themes, for e.g. on Ubuntu. Screenshot attached with an arrow showing the button

P.S. Couldn't find an existing issue.

[sy-be]

I actually spent 5-10 minutes to move tabs back to the side, I was searching for the option in menus (View), in addon preferences, in toolbar actions - couldn't find anywhere. So I think it would make sense to add an option to View menu too.

[fvsch]

Can confirm this issue. Problem is that the checkBrighttext function in VerticalTabs.prototype.init looks for the the brighttext on the #nav-bar toolbar, but the icon is inserted in the #TabsToolbar.

In this case, the tabs toolbar has the brighttext option, but the nav bar doesn't, so the wrong image gets picked.

That being said, when I tried to change it for #TabsToolbar, it didn't work on the browser's load. It only worked on later executions, such as toggling the vertical tabs on then off. Looked like the first time checkBrighttext() is ran, the #TabsToolbar doesn't have this attribute yet.