When I create a new parameter using the What If feature in Desktop, I can add a slicer to the report canvas. but I can't change the slicer to a list. This seems to be a bug. see video attached
I have reported this issue internally: CRI 94215204. Will keep you update once I get any information.
Best Regards,Qiuyun Yu
The fix will be part February Desktop release. Should be in service January.