Disable Microsoft Edge (Chromium) developer mode extensions pop up at startup
I found a patcher that works - https://github.com/Ceiridge/Chrome-Developer-Mode-Extension-Warning-Patcher
I can confirm that the patcher is currently working.
As a side note the patcher has been updated 3 days ago and I did not have to tell it where to find the Edge installation folder or do any renaming of files, it worked great on auto install. New tabs, new windows, and new instances all come up with the warning disabled.
If you get Edge Dev or Canary instead of Edge Stable or Beta, the extension warning will go away. If you are already using Edge Stable copy %userprofile%\AppData\Local\Microsoft\Edge\User Data\ to %userprofile%\AppData\Local\Microsoft\Edge Dev\User Data\ and everything will transfer over.
Get Edge Dev or Canary from https://www.microsoftedgeinsider.com/en-us/download/ (DO NOT get Beta, as that has the extension warning)