[rmurri]

I don't know about TST, but sidebery can alter your window title when it's active, so you can match css rules against it.

    #main-window[titlepreface*="Sidebery"] #TabsToolbar {
      visibility: collapse !important;
    }

[syncbehind]

Oh heck! That's rad. I'll have to play around with that. I use sidebery so this is aces. Thank you!