There is an option to Group Dashboards by using #hashtags in the dashboard name.

This comes in handy when you have a lot of themed dashboards, for example, several dashboards for the #IT department containing #monitoring of #virtual-machines, #switch-metrics, and #open #incidents, or for #marketing and #sales departments, you could have #client-revenue, #active-campaigns, and #open-leads dashboards.

To add a #hashtag to a dashboard, click on the Edit icon on the right of the dashboard's name, and simply append a new hashtag to existing ones (while in Edit Dashboard mode):

After saving your dashboard, you will find the #hashtags and the related dashboards on the Dashboards screen:

The #hashtags on the right (under the search box and Favorites) are clickable. Clicking on them will filter the dashboards in the list to contain only the dashboards that have the clicked #hashtag in their name.