According to the manual, the joystick press on this wheel acts as a Simucube Button and allows for FFB modification on the fly. Are these modifications permanent and saved to the current profile or are they only temporary and after turning off the wheelbase, FBB will revert to settings from the profile?
Any changes are not saved into your FFB settings profile.
So after restarting computer everything should default to profile settings, right?
yes, that is true.
Also just re-applying the same profile from True Drive will apply those settings again.