Users can mount their PAT tokens inside workspace by following this section in the documentation:

https://access.redhat.com/documentation/en-us/red_hat_openshift_dev_spaces/3.5/html-single/user_guide/index#using-a-git-provider-access-token

1)

Consider adding UI for this process which would simplify this. It seems there is already issue for it:

https://github.com/eclipse/che/issues/22112

In this UI consider retrieving che-userid automatically, so user don't have to.

2) If technically possible, consider dropping the requirement of providing scm-userid , to make the process even easier.