It is possible to add pre-prepared queries and even whole dashboards from the public Dashboard repository.
Simply go to the "Dashboards repository" page (on the right of the main toolbar)
The queries and dashboards are divided into categories, you can browse the list for each one.
To copy an item to your account, click on "add query/dashboard", which will copy the item and open the editing page. You can make adjustments or leave it as is.
The copied query will now be available on your account's query's list. You can find it by clicking on "Queries" in the main toolbar.