Have you tried this
Did you try a dual axis and instead of Line, you use circles stacked on it? That's one way.
I'm sure you did that. Here's the next way.
Drag and drop DATE on your PAGES. Then open the settings.
You're going to want to play around with this box called 'Show History'
Or try this calc and add to detail
if last()=0 then 1
elseif first()=0 then 2
Find more ---->Dotted Line Charts
Please mark the answer as HELPFUL/CORRECT if it really helped you so that it can help others as well , help the community back
Unfortunately this is about the closest I think you can get to the solution - its a dual axis with bars in measure names, then line on the dual axis, and a reference line approximating the dotted line you were after.
But I'm questioning why you need to mark the value as a dotted line, where I come from dotted lines are only used in treasure maps, and in your case, you could use a light grey tone to denote something you aren't really meant to look at, or use the tooltips to indicate the actual value.