GPO StartLayout Never Applies
Solution 1:
The changes you're making are to the default profile, and as such will only apply to new accounts. You'll need to delete your profile and log in again in order for the new StartLayout to apply to your account.
There's a fair amount of information here: https://www.joseespitia.com/2016/06/27/customized-a-windows-10-start-layout/