Hi there!
If you add the Users Table to your app, you should be able to access the properties present in Settings → Users → Custom Fields, from your Connector function (so long as it is the right data type).
% In trigger
Run Connector Function -> Connector -> field: Table Record -> Users Table -> Email
You can go about loading into the user record in a variety of ways (interactive table, single select dropdown, etc.).
Unfortunately, to access the user name you’ll need to use a workaround. You can view some of those here: Extract User Name Text from User Table