My understanding is the Tooltip action filter to apply
almost in the same fashion as a Cross-Datasource filter.
If the other datasource has fields of the same Name / Type
(and at least some values to be the same in both), then
a Tooltip filter would be triggered and applied seamlessly.
Please find the attached as a simple demo of the above.
If I miss your question / purpose of the topic, please reply.
I've seen that already. I don't have common field names.
Here's what I did though. I put the sheet I want to use in the tooltip on the dashboard. Hidden. tiny. Nobody sees it. Then I made a hover filter action so that it get's set the way I need it to be. Finally I put it in the tooltip, and the correct viz from mark to mark appears.
I don't have common field names
You can make the same name copies in both.
And you're right, hover on dash would work, too.