Remove 'Search Bing in sidebar' using policy, startup flag or registry

Hooray! Once the https://www.microsoft.com/en-gb/edge/business/download?form=MA13FJ Definitions https://learn.microsoft.com/en-us/deployedge/configure-microsoft-edge#add-the-administrative-template-to-an-individual-computer, you can set it as follows. I have set it at the Computer Configuration level in this case.

Super happy this has been implemented!