Are there any built-in Health dashboards which can provide us
1. The usage stats by users.
2. # of concurrent sessions running over a day timeline
3. Usage of each dashboard, ad-hoc Search
I have a few example searches in Alerts for Splunk Admins https://splunkbase.splunk.com/app/3796/
The platform access report can find dashboard usage...I also have some around logins.
Or you can of course build your own searches to do this...