I'd like pressing backspace to step one level up (outside) in a directory hierarchy instead of going to the previous opened location. How to configure this in Thunar?
You need to have editable keyboard accelerators turned on as documented under "How do I assign different keyboard shortcuts?" on this page*. Then hover over menu Go->Open Parent and press backspace twice.
That should add this line:
to your ~/.config/Thunar/accels.scm
*This setting is also exposed in the Gnome Configuration Editor under...