Ah you have found a bug !
When the dialog is loaded it is initilializing the Rename File Part Only with the value of Simplify non-standard characters, sorry I will get that fixed.
All changes made from the defaults are stored in songkong.properties (not the one in the install folder but the data folder see Help for OS specific details) so yes you can edit and reuse them. But It won't resolve this particular issue, currently the only way you can get it to default Rename File Part Only to Off in the regular desktop UI would be to set Simplify non-standard characters to Off.
Alternatively you could use the Remote (web) UI, this does not have this bug.