Parameters - default value SQL for Dashboard filter

I have added a parameter to my view:

anchor_date of type date without default value

then I added a dimension to get around the lack of support for programatic default value:

selected_date of type date with SQL that takes anchor_date or if it’s NULL it takes CURRENT_DATE

Now I have a dashboard with couple of looks created using that view. I would like to keep the selected_date as hidden dimension because it’s only used in calculations or liquid but dashboard filter is behaving weird.

If I select anchor_date as filter I can’t remove default value but in order to be able to choose selected_date I have to remove hidden = yes from the view…

Also I realised I can’t really use selected_date as filter because then it gives people all the filter options like in the past, in range, but SQL won’t accept it, it has to be just one single date