I’ve created two monitor profiles:
Profile 1: All 8 monitors active
Profile 2: Only 4 monitors active, 4 monitors disabled

When switching to Profile 2, the deactivation does not work correctly:
 Only one monitor (seemingly random, usually Monitor 4) gets repositioned from the right side to the bottom-left corner instead of being properly disabled.
 (See screenshot No.3 for reference.)

Both Windows and the DisplayPort connections have been restarted, but the issue persists.

Have you tried disabling/enabling the monitor in the Monitor Configuration interface? I can't even use that now — I can only turn the monitor on/off through the default Windows interface. So when I switch profiles, the enable/disable setting has no effect at all either.

Correct, it is just as you said.
In DisplayFusion’s monitor configuration, you can only set the position (I haven't tried changing the scaling or resolution),

and it can only be enabled or disabled through the standard Windows interface.
Switching profiles has no effect.
So this seems to be a general DisplayFusion issue.

I wonder why the support team has not yet responded.
Greets

I'm not quite sure if this is related to Windows' Win+P display modes.

I have three physical monitors and one virtual monitor. I noticed that if I use the Windows interface to disconnect the last three monitors, and then check with Win+P, it shows "PC screen only."
Conversely, if I disconnect the first three monitors and leave only the last one, pressing Win+P will show "Second screen only."

However, if I use DisplayFusion to switch profiles and the switch fails, I can see that the Win+P mode remains stuck on "Extend."

I did a few more tests — currently, switching to only enable the first monitor usually works, and switching to enable all monitors also works. The one that typically fails is switching to only enable the last monitor (which is the virtual one).

I'm not sure if it's because it's the last monitor, or because it's a virtual monitor.