How can I revert / rollback the Windows 10 Start Screen after I make an error (using Partial or Replace mode)?

Use Netwrix Endpoint Policy Manager (formerly PolicyPak) Script manager to run a simple script to re-trigger the initial start menu layout. Note you may not get an EXACT revert; but it's pretty close.

Endpoint Policy ManagerStart Screen and Endpoint Policy Manager Scripts: Specify exact Start Menu experience one time