It is possible to add pre-prepared queries and even whole dashboards from the public Dashboard repository.
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Simply go to the "Dashboards repository" page (on the right of the main toolbar)
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The queries and dashboards are divided into categories, you can browse the list for each one.
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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.
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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.