We also have a similar feature in our company but we directly view the scoreboard on the power bi service itself.
The basis for this form of dynamic row level security is that the expression written is evaluated for each row in the indicated table to either True or False.
If your user has signed in to the you will be able to determine the identity using USERPRINCIPALNAME(). This is the email address they use to sign into the service.
Since you are displaying data specific to that user, it is possible you already have their email in your data. If that is the case, and it is simply another field in your table your validation line would look something like:
'Table1'[Email] = USERPRINCIPALNAME()
The left side of the expression refers to the row you are referencing, while the right will supply the name of the authenticated user.