I just tried it and it appears there is no hiscore.dat in the PND and the hiscore.dat location is set to usr/local/share/xmame/hiscore.dat.
The hiscore_file variable (sets location of hiscore.dat) needs to be added to mame.sh (inside the PND) as :
OPTS="$OPTS -hiscore_file ."
And then rebuild the PND.
This should allow hiscore.dat to be placed in the mame.106 appdata folder and be recognized.
OR
I did:
usr/local/share/xmame/hiscore.dat (where the default config points to in NAND)
1. Create the usr/local/share/xmame/ directory stucture in NAND (use " sudo mkdir -p /usr/local/share/xmame/ " in terminal)
2. Change the owner of that path to your account (use " chown -hR your_account_login_here /usr/local "
3. Copy hiscore.dat into usr/local/share/xmame/ (use the GUI file manager or terminal)
And now it saves high scores to the appdata/mame.106/hi folder
This ~190k hiscore.dat file is read-only so it shouldn't harm the NAND.
Get hiscore.dat from
http://highscore.mameworld.info/download.htm
Extract the hiscore(pre_mame0133u1).dat file from hiscoredat.zip.
Rename hiscore(pre_mame0133u1).dat to hiscore.dat and copy it into usr/local/share/xmame/
No promises, but if no one else does I'll probably have a look at integrating Pickle Launcher into this port and rebuild the PND.