Any chance of putting these planes into a part file of any kind? Simple task at that point.
you can do it using a 3d sketch. Draw a line, then connect that line endpoints to each plane.
Cool, then I could include the 3D sketch into a 2D sketch to keep the relation to a sketch used to create a tab of a sheet metal part.
AKA: There is no method to do this directly into a 2D sketch, right?
The issue I'm trying to avoid is having a dummy part to hold the lines location.
I want assembly planes driving part sketch's creating parts. I avoid part's driving sketches until it is required. Typically this is required when parts (sketches) are driven the gages of another parts material.
This relates to a case where the angled plane is another part(gage) edge driving another parts size in relation to another plane. but in this specific case, I don't have an existing edge where the planes intersect.
"Any chance of putting these planes into a part file of any kind? Simple task at that point."
I did that first time around, but that takes extra work because I needed a placeholder part. Exactly what I'm trying to avoid.
If you wanted to do it only in 2D sketches, you could draw a horizontal line in plane 1 and then on a sketch on plane 2 you can pick the pierce point on that line where it intersects through the plane (or vice versa, can't remember which way round you described it.
I don't see how a coordinate system would help. The Idea here is the size and location of a tab sketch moves relative to the location of two planes that are not 90 deg to each other.
Using either the 3D sketch or pierce pint method can both get it done using one sketch to get geometry on one plane that can then be used to locate a 2D line on a second sketch.