Updating NR reporting using variables

Summary:

I have about 6 NR reports that needs to updated to a different monthly scenario every month for reporting the MEC. I thought about creating a substitution variable in my freeform EBPCS app that my reports are connected to, however, I do not see the variable in NR. I've also logged out and log back in. Is there an easy way to update NR report scenario monthly? Is the best solution Sub Variables? if so, is there a reason its not showing up after creation?

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