Both web dashboards and custom tabs display the results of data lists. When you create a web dashboard, however, there is an option to create one with a context record type of <None>, and if you create a dashboard of that type and a data list with no context record specified, you can display it successfully on the dashboard.

However, when creating a custom tab by turning on Design Mode and then clicking on Edit tabs and then Add to add a new tab,  and then Edit section to populate the new tab - When I change SectionType to DataList, under the Data List section, I can search for and choose a Data List with no context record. However, immediately below the DataList search field is another field called ContextType. The only choices available are PageContext, PageExpressionField and Expression. 

It would be extremely helpful if Blackbaud could add an option under ContextType of <None>, as they have added when creating a web dashboard.

This would be highly beneficial to us. Often what would be most useful in a custom tab is just the straight up results of a Query/Data List, without filtering for only records that share a common context record. As an example, for our Finance department, they need to be able to see all financial transactions in CRM, regardless of campaign, campaign year, designation, etc. To have this ability would enable us to create custom tabs to show all sorts of data that we currently cannot.