I figured out how to create playlists on my Mac and put them on the AK100. It's a bit of a PITA but it works.
First, I use Markspace Android Sync to copy the iTunes playlists and music I want to my micro SD card. I first set that up to tell it the types of files that can be played, as the default doesn't include m4a, and others. This re-creates the playlists in a folder/directory named Markspace/Playlists on the SD card and puts the music in Markspace/Music.
I open up those playlists in BBEdit and change the paths from "../Music" to "/mnt/SD0/Music" (Note! This is the bottom card in my player. If your card is in the top slot, change SD0 to SD1.)
Then I eliminate all the M3U lines using the find and replace option with "grep" in BBEdit, as those lines all start with "#EXTINF:-1". Specifically, searching for "#EXTINF:-1.*\n" and replacing it with nothing.
I save the files to "AK100/Playlists".
The problem I had then was that even though the path listed for each file was correct, the AK100 had all the entries in each playlist greyed out. This stumped me, but on examining the file I made compared to a playlist made by the player, I found that the AK100 wanted CRLF (Windows) line endings, not LF (Mac).
Playlist 1.pls: ASCII English text, with CRLF line terminators Radio Nights.pls: ASCII English text
"Playlist 1.pls" was made by the player. "Radio Nights.pls" is one of my converted playlists.
The solution was BBEdit's Text Factory (File -> New -> Text Factory) which can batch change encodings and line endings. Changing all the files to CRLF allowed them to be read properly by the AK100.
Now I just have to script this lot and I can auto-fix it all the next time I run the Markspace software.