The Problem:

I recently fired up Konsole and tried using tmux when I suddenly realized that Control-B wasn’t working.

Plasma, in one of their recent updates, seems to have added an “Add Bookmark” global shortcut to all Plasma apps mapped to Control-B. While it’s active, Control-B in Konsole won’t get sent to tmux, but will instead keep adding bookmarks to the Konsole Bookmarks menu.

The Fix:

Open System Settings
Under “Workspace” choose “Shortcuts”
Select “Standard Shortcuts”
Find “Add Bookmark” in the list
Change the Shortcut to Custom, then don’t assign a key sequence. This will set it to none.

Once changed, tmux should immediately start working again