Filter widget not populating drop down selection box correctly

[JonathanHall3]

Hi I'm using the filter widget in ArcGIS Experience Builder.  When setting the filter up, I'm asking the user to select a value from a pre-defined list in a drop down box.  So in the SQL wizard under 'select source type' I'm selecting 'Unique - pre-defined'.  And in the next step to predefine unique values, I'm selecting the default 'all'.  This gives an SQL statement as '(Type = ?)'. However, when checking the filter box in the preview, the selection box is just populated with 'all'.

[JonathanHall3]

As an update to this, in the SQL expressions I am selecting 'is' as an operator, then I notice that under 'select source type', the multiple (pre-defined) option is missing.