Select the typ of list you need (Field,Variable,Flag or Date Range Picker)
Enter a reference to:
Field - Any field or an expression that works as a dimension
Variable - Has to be an existing variable created either in the script or the gui. Selectable variables are entered in a comma separated list.
Flag - Select a field that has a country name corresponding with the flag names. (Has to be a perfect match with the flag name so check the list of flags if you are not sure.)
Date Range Picker - A field holding a date field with a "complete" set of dates. (i.e. no gaps in the timeline) For this to work you need to set a correct variable. Typically this is a variable "vToday" which is set to "=Today()" but the idea is that for instance "=Today()-1" can be used to offset the starting date for the calendar by one day.
Add a field label
Add an initial selection if you want. This will also work with expressions such as "=Year(Today())-1".
You can set initial selections to be updated once per session or every time you move to a sheet.