OK, one last point on this. I finally fixed it for real, since the Trigger option kept malfunctioning after a restart.
To enable command + shift + ? for TT, you first have to disable it for Help in ~/Library/Preferences/com.apple.symbolichotkeys.plist. In there, one of the entries will use 44 (which is either / or ?’), you can then change which hotkeys trigger the Help command. Even if this entry is set to enabled = false, TT will still read it as a used command. After changing the plist, don’t forget to restart.