Thanks in advance!
If its greyed out, that means it hasn’t been mapped for the current stream/data source you are working in. Hope this helps.
To follow up on @ShaneAngel 's comment, it won’t fully disappear until you actually un-map all data sources/streams from the button. In your case, my guess would be that there’s a column in your “Schedule Date” stream that is still mapped to that dimension.
Thanks tim.janes and @ShaneAngel for all of your replies! I believe I was looking for Unmapping. I’ll try it out.
I had a thought after my post that you might have meant getting rid of it the other way, lucky @tim.janes was here to help