It would be nice to have an "Apply" button for parameters as well like filters do. Unfortunately the idea is still open. In your case, see if you can use filters instead of parameters where ever possible. This way you'd be able to include "Apply" button.
It would be useful when user has to select between date ranges and every time users selects one date tableau starts processing it. I'd also be curious to see if someone has a work around for this.
Unfortunately need Parameters as they have to be passed to several calculations and used in complex formulas.
That's what I was afraid of.
Unfortunately Andrew is correct and I have exactly the same issue myself with one of our dashboards.
Server and Desktop do have the Calculation Pause/Resume control
So I could theorize that if this could be accessed via TABCMD or REST API, you might be able to pause it while people enter the parameter value and then restart. We've not looked at this, so no idea how feasible it is.
There is also this method from Jonathan, a while back
but with multiple parameters and the extra data modelling work, we decided that the "juice wasn't worth the squeeze" (as they say in the US!)
I've voted the idea up...surprised it's only got a handful of votes.