Wondering the same over here! The only workaround I could imagine is to use an absolute positioned rectangle with the shadow color you want as a fill and blurring it out
Yet this makes absolutely no sense in the long run and it would just be quicker to just let us use variables (and color styles too!) in shadows as Hampus said (coming soon)
This workaround totally makes sense! I gave it a shot, and this “fake shadow” looks just like the real shadow and it works when I apply themes. I’m gonna use this workaround as a temporary solution until they begin supporting shadows in variables. Thank you for that!