Please explain the motivation behind the feature request.
When adding a custom extension, the popup closes and then it tries to activate it, but if it fails, the user has to go through the process of filling out the popup again, which becomes insanely tedious with more than a few environment variables

Describe the solution you'd like
The "Add custom extension" popup stays open until it tries to activate it, and on success it closes and moves on, but on failure it stays open, shows the error message, and allows the user to make any settings changes before trying to add it again

• I have verified this does not duplicate an existing feature request