I've read about how to group JPG and RAW in digikam but I still did not find any good practice for me.

My folders are as follows:
YYYY
YYYY\YYYY-MM-DD
and so on.

My first try was to select all the pictures in the first folder YYYY\YYYY-MM-DD and grouped it by name.
This worked fine, but to select all these folders manually I would need more one hole day of work just for the default grouping.

My second try was to select "View > Include album sub-tree" and tried to group all pictures of one year in one step.
Unfortunately this didn't work, the pictures got no grouping.

So at the moment I'm having 2 questions.
Why is the grouping working if I'm selecting the lowest folder but not working if I'm selecting a higher folder.
How is the best practice to group JPG and RAW for all of my pictures without spending hours just for this one simple step.

Walter