How can I enter identical information in multiple fields at the same time?

I want to add information to tags from folder names
%artist%\%year% - %album%\%dummy%
how can I add an album and an albumartist at the same time?

only with a second step where you add the information from the existing field to the new field.

So there are no instructions in one operation? Two of course I do

Using a action group with 2 subsequent actions does this job for the user.

As you do 2 steps (1: extract the information, 2: duplicate it), it also has to be done in MP3tag with 2 steps.