Just a feature request to use the extra buttons on 5-button mice (and greater) to navigate back and forward. Just like web browsers do. Especially useful for the pathbar style. In case there was previous feature request, for the record, I couldn't find it anywhere and Gmane sent my feature-request posts to '/dev/null'
There's already a hidden option MiscHorizontalWheelNavigates, which should do what you want. Check README.thunarrc.
Resolving to INVALID as the requested functionality is already available.