I have faced this issue a few times now and accepted the probability that it is not possible in Looker. Now that a new, similar, request rises again, I decided to ask it here.
I would like to make a Chart that stacks some values in columns, but put one (or more) values as a line along the stacked columns as seen below.
This combination of columns and lines seems to be only possible with Grouped columns, as seen in the image below.
Does anyone have an idea if this can be done?