Can BetterDisplay keep a desktop available when my KVM switches away?

A connected virtual screen can keep a desktop available to macOS while the physical monitor is disconnected by a KVM. A BetterDisplay EDID override changes display information. It cannot keep a physical connection present while the KVM disconnects it.

One approach is to work on a virtual desktop and mirror it to the monitor while the KVM connects that monitor to the Mac. When the KVM switches away, the virtual desktop can remain connected. This can reduce disruption. Some apps may still move windows, and the physical monitor may take time to reconnect.

Create and connect a virtual screen with a suitable aspect ratio and desktop size, then configure the physical monitor to show that virtual desktop. Configuring mirroring in BetterDisplay requires Pro.

If you use the Pro association features, open Settings > Displays > [virtual screen] > Associated Displays > Association Settings…. Leave both Auto-connect virtual screen and Auto-connect virtual screen when all associated screens are offline off so those policies do not disconnect the virtual desktop as the monitor comes and goes. Enforce virtual screen mirroring can restore mirroring to the associated monitor when it is available.

The two auto-connect policies serve different purposes. Ordinary auto-connect keeps the virtual screen connected while at least one associated monitor is online. The inverse policy keeps it connected only while all associated monitors are offline. To keep the virtual desktop connected through the whole switch, leave both policies off. See Associated Displays for those policies.

Keep another usable display or viewing method available while testing the setup. Windows placed on the virtual desktop can remain there while the physical monitor shows the other computer. Picture in Picture can show that desktop on another Mac display, but requires Pro and Screen Recording permission.

Follow Keep a desktop available while a KVM switches away from your Mac for the policy order, initial mirror setup, return test and targeted cleanup with an independent recovery screen.

Test switching away and back with your usual apps before relying on the arrangement. If you need the Mac to retain the actual physical display connection, that requires appropriate KVM or hardware connection-retention behavior. An EDID override alone is not a substitute.