Getting X Y coordinates relative to a subplot

Hello everyone,

So I have an issue where I have a figure with multiple subplots, some spacing in between them. In between said subplots I would like to place a text annotation at a specific location, say under a particular vertical line. The problem is that I don’t know how to get the x coordinates of that subplot’s line relative to the entire figure. What I’ve done so far is manually check where the annotation goes when I set its x coordinate to varying numbers between 0 and 1 so that it lies approximately where I want it to. Ideally I’d like a more methodical approach to this, and am wondering if there is a specific method that would take care of the trick for me. Anybody happen to know?