Just bumped into this limitation myself.
My machines have Duet3D boards and the latest firmware required text string parameters in double quotes for the dynamic acceleration M593 command. I've been using scripting to disable M593 dynamic acceleration and M572 linear advance when printing infill and support because it slows down the printing process and I don't care if those features have ringing artifacts.
Sounds like a worthwhile feature request if V5 ever becomes reality.
