This tutorial covers how to display a member's current plan in a pricing table. Preview link.
At a high level, you will need to add "This is your current plan" elements to your pricing table, create gated content in Memberstack, and then give the "Current plan" elements the appropriate data-ms-content attributes.
The video covers setting up a pricing table with all paid plans and a pricing table with one free "plan."
[If I haven't shared the clonable link by the time you read this, please leave a comment.]