I haven't heard of any freeware GUI tools around FBWF beside MS fbwfmgr (connand line tool).
Perhaps, with the FBWF API it is easy to create one (for instance, something like EWFTray from www.xpefiles.com would be extremely
easy to port to FBWF).
There is FBWFTray GUI utility on sourceforge but it was created for BartPE. Don't know if FBWF lib there matches the one from XPe.