SAP Analytics Cloud - Dynamic Row level Security

Can someone please tell me a why to implement row level security in SAP Analytics Cloud.

So depending on the user logged into SAC they should only see particular record for them. I know about Data Access Control but it has to be done manually where I assign each user/team to each row which will not work since we can have >10000 users and they will be increasing over time.

I have also seen the Current user() dynamic text to identify the user but I am not sure how we can pass this back to the model to filter the data.

Input data Source - Flat File,