Here’s a good one: Andrea Stastna asked on this thread: RUNNING SUM in detail (Tooltip) (tableau.com) how to achieve a tooltip that increases as you roll across a selection of months, so as you hover of January, only January shall appear in the tooltip, similarly, if you hover over May, then all 5 months from January to May shall present
Create an integer parameter to hold the month number: Jan = 1, Feb 2 etc
Create a boolean index() function scoped to the month, so Jan = 1, Feb = 2 March = 3 etc and as part of the calculation, set as Index() < parameter +1. Performing a less than calc evaluates faster than <=
Now move your Index calc to the filters selecting True. This can be tested by materialising the parameter and manually updating the values
On your primary sheet set the filter on the tooltip either to: fields="" for no filtering or, if you have items to filter, add these instead
In the worksheet actions, set a update parameter action, set the action to hover, target your parameter and set the month of your date, ensure this is min (or max) therefore only the month number shall be captured.