I'll describe my scenario. 21 area managers want a dashboard showing data relevant to their area only. This data is a subset of a larger data set (ie I have incidents recording for a whole town, each manager just wants their areas data). We do not want them to be able to see each others data. I can do this by creating 21 separate dashboards each pre filtered to their data only, but this would be frustrating when any functionality changes are required as I'd have to repeat the task 21 times.
Is there a way for them to essentially access the same dashboard, but the data is filtered according to their user?
I haven't worked with the URL parameters but that is probably your best option.
https://doc.arcgis.com/en/dashboards/create-and-share/url-parameters.htm