power bi report builder - parameter property - "allow blank value"

Mmm somehow the only reponse got upgraded to 'Solved!'  Hilarious, wasn't me.

Anyway still no answer to the 'Allow blank value ("")' property nor documentation.  All my parameters have 'Allow multiple values' set.   So maybe that is the issue, when not a multi-value parameter then the setting does something exciting :}

I have decided to as a work around to set

'All' to mean give me everything including blanks. 

'NA' to mean 'blanks'.

'blanks' can be any of  blank, null, 0, ‘Select’, ‘NA’, ‘Not Applicable’, "", " "  as there is lots of interesting data :}