We are slowly moving ahead in the Directory Art process. I’ve seen a batch of tools/apps people have been using to help in the convoluted process of making DirArt.
I use PETMATE for most of my editing needs, sprinkle a bit of Marq’s Editor, javascript functions and cc1541.
One of the main reasons for Marq’s Editor was that it had a visual way to show the charset changes in the directory art versus standard PETSCII.
Don’t get me wrong, Marq’s is a great tool, but I prefer PETMATE as an all purpose PETSCII editor. PETMATE needs better DirArt support, but I figured out a way to make life a little easier in PETMATE for DirArt..
I took a copy of the uppercase rom for the c64 (c64_upperfont.bin) then :
printf '\x'92'\x'49'\x'24'\x'92'\x'49'\x'24'\x'92'\x'49 | dd bs=1 count=8 seek=$((0x110)) conv=notrunc status=none of=c64_upperfont.bin
printf '\x'92'\x'49'\x'24'\x'92'\x'49'\x'24'\x'92'\x'49 | dd bs=1 count=8 seek=$((0x400)) conv=notrunc status=none of=c64_upperfont.bin
printf '\x'92'\x'49'\x'24'\x'92'\x'49'\x'24'\x'92'\x'49 | dd bs=1 count=8 seek=$((0x468)) conv=notrunc status=none of=c64_upperfont.bin
printf '\x'92'\x'49'\x'24'\x'92'\x'49'\x'24'\x'92'\x'49 | dd bs=1 count=8 seek=$((0x4A0)) conv=notrunc status=none of=c64_upperfont.bin
... the rest of illegal PETSCII chars...and inserted a few magic bytes at the beginning 0x00,0x38 and renamed it DirArt.64c
So this file is compatible as a font file for PETMATE. Which lets you load it in and show you what chars are illegal in PETSCII for Directory Art 
Here is font file, if you want to try it out: