Usage of "insert member formula" in smart view

Summary:

What is the functionality of the "Insert Member Formula" button in Planning Ad Hoc (Smart View) and how do you use it?

Content (please ensure you mask any confidential information):

Hello, I've tried googling and searching across both docs and CCC to see if there is any explanation of how to use the "Insert Member Formula" button in Planning Ad Hoc, but cannot find anything that seems to answer my question. Enabling it and clicking it doesn't really do any anything - could someone please explain the intended functionality for me?

Many thanks.

Version (include the version you are using, if applicable):