If you need to show different fields to different (types of) users in your portal child form, you can often use conditions based on either the linked record field used to link the records to the user itself, or a lookup field derived from it.
For example:
Your users table is linked to a "Submissions" table.
You want to show the "Approval" field in the submissions table only to supervisors.
In your "Submissions" table's child form, make the "Approval" field conditional.
Either use the linked record field that connects the user in the condition (e.g. "If User is John Doe", note that you can add multiple users by adding multiple "or" conditions) or
Add a lookup field to the "Submissions" table that pulls in the "User Type" field and use that in the condition (e.g. "If User Type is Supervisor").
This setup works well when each record is only linked to one user in the same linked record field. If each record can be linked to multiple users, we suggest using different portals with different access rules for the different user types.