Last tested: May 2021
You can't see this in the UI at the moment, but you can use the
dashboard explore in System Activity to see the created date of each dashboard element.
Note: Make sure to replace the [HOSTNAME] above by your company url, and then filter on the proper dashboard ID!
If you need to know which element ID corresponds to which query, you'll have to use the "get dashboard" API call.
There is a feature request you can vote for to add this metadata on the system activity explore: Identify who edited a dashboard directly from the content