DMD config redirected by DMDDEVICE_CONFIG
What it means
DMD changes made in the VPinMAME folder have no effect.
Why it happens
The DMD driver reads the file named by DMDDEVICE_CONFIG before the one next to it; its installer sets this variable (dmd-extensions README and Configuration.cs).
How Pincab Toolbox detects it
The DMDDEVICE_CONFIG variable names an existing file, inside the scanned install, other than the dmddevice.ini in the VPinMAME folder, which also exists.
Check your own pincab
Pincab Toolbox is a free Windows scanner for Visual Pinball X and PinUP Popper. It finds and explains problems like this one. No account, no telemetry.
Download for freeCovered: Visual Pinball X (10.x) and PinUP Popper. Not covered: Future Pinball, Pinball FX, Visual Pinball 9 and the other frontends (PinballX, PinballY).