How can I change / edit a user's email?

That doesn’t make any sense. Even if email acts as a unique ID, you should still be able to change it as admin during or after creation, and prior to password/email verification, without asking each user change it from their end--which is impossible to do if you’re setting up a new account and make a typo, OR when connecting a HS Sandbox to a SF sandbox. SF sandboxes set all users with inactive/“fake” emails appended with .invalid by default, and to properly configure your HS Sandbox to connect to your SF Sandbox, you need to be able to create emails in the form of “username@yourdomain.com.invalid” (most of these users will never login and you will never set their email to a real email; but HS has to match SF). I’ve tried deleting HS users and recreating them with .invalid emails to match SF, but it seems HS just fails with “There was a problem creating your user(s). Please refresh the page and try again”, EVEN if you check “Do not send an email invite when this user is added to HubSpot”.
How are admins supposed to setup a HS Sandbox and connect it to our SF Sandbox if we can’t even create matching users or change their emails to match our other sandbox(es)???