I want to be able to use or not use an "Allow multiple values" parameter. So far, all I've found is how to add "blank" or "null" as a parameter default, but that only pulls all the values that are blank or null into the result set, it doesn't allow me to skip the parameter.
Also, I do not use a subroutine solution or "Get values from query", I allow users to type the list manually in a comma separated text box as (myFirstParam) with no settings and use a second dummy param (mySecondParam) checked to "Allow multiple values" with Default Specified value: =SPLIT(REPLACE(myFirstParam," ",""),",") and in the dataset query add: WHERE myField IN (@mySecondParam). I had to add @mySecondParam in the dataset parameter list, using the specified value as the expression.
If another solution is better, I will try anything, as long as data values are manually entered and entry is optional.
Thanks for any help you can offer.