Super Easy! Upload your data using "Create Feature" in ArcGIS Online. Then you can drag and drop in your .csv.
You can also publish your .csv from ArcGIS Pro directly to your contnet in Online. Using the sharing features.
Then, when you're building out your dashboard, you can simply browse to the dataset without commiting the table to your actual map that is featured in your dashboard (if there is even a map).
^ You can get to this when you are 'picking' your data in the dashboard builder.
Let me know if this answers your question and I'll holla back if you have more.