In a portal child form, you can use conditions based on the child record’s linked user or a lookup derived from that user. These conditions use the child record’s field values; they do not automatically use the role of the person currently viewing it.
For example:
Your users table is linked to a "Submissions" table.
You want to show the "Approval" field on submission records linked to a supervisor.
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 is appropriate when each record is linked to one user and that linked user is the one whose values should determine field visibility. If each record can be linked to multiple users, we suggest using different portals with different access rules for the different user types.