How to add negative price on Unreferenced RMA Order line

Summary:

Got to know that current pricing functionality does not support Returns Price Lists.

Could you please advise how to introduce negative pricing on order lines for Unreferenced RMA Order lines.
Tried by creating a new standard price list also but not working.

Content (please ensure you mask any confidential information):

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

Code Snippet (add any code snippets that support your topic, if applicable):