NeophyteNeophyteNot at DataSource, but you could look at the "Azure Site Recovery" official EventSource. This uses the "Azure Log Analytics Workspaces" collection method, which has a kusto query configured.
I asked support about whether it was possible to use that collection method for our own custom EventSources. They said it wasn't supported. I played around with returning different fields, but with it being undocumented and support being evasive i gave up.
Maybe it is the same situation with the DataSource, it has the option to configure a query, but no information on how it is supposed to work.