D365 Ribbon Workbench subgrid button not visible

I have a D365 form with two subgrids. I have to add a button on one of the subgrid.

I'm trying to achieve this using ribbon workbench, but facing issues.

Issue 1: How to specify the subgrid on which i want to show my button?

Issue 2: Right now, button is not visible on either of the two subgrid.

Please suggest any solution.

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