in answer to your first question, I would turn the solution on its head. Instead of selecting no regions I would use the dropdown to select all Regions and then use a IN command in the filter statement, which would look like this:
FILTER "table"."regions" IN (<%= regions variable %>);
That way only cases from those regions will be used that are selected, however many are selected. If all regions are selected then there is no restriction and all cases are included.
Its important that the dropdown button has the following settings:
Allow multiple selections is activated
The Separator is a "," (comma)
The wrapping Characters are “’” (single Quotation marks)
When you publish the analysis make sure all regions are selected in the dropdown so that this become the default that viewers see when they open the analysis.
As for your second question about writing “All Regions” when there are no restrictions on the regions displayed, I’m still working on that and will try to post a solution soon.
Calandra (Celonis Data Science Team)