This is a candidate for the top down design process. You would make the edits in the assembly with the 45 degree tube active. You can use the vertical tube for its diameter reference, location, and even the projection plane.
Just remember that you now have a dependent reference. You can unlink it manually when you are back in the 45 degree part but sustainability is a nightmare. You have to decide if top-down design models are acceptable in your organization.
You can also consider a skeleton model that holds all the tube centerlines. In this way, you can reference only one model for all your assembly references in lower level parts. This is normally much preferred since you will minimize the number of dependent files to 1 (+assembly).
I am working on a bike frame myself (a reverse engineering session for posterity) and I am not using separate tubes. I am modeling the weldment at a part level. If I need tube prep drawings, I would use assembly cut to cut up the master part into the individual pieces. This may seem backwards, but in this way, the "master" is a part file with the prep'd tubes as subordinates rather than masters. In this way, I am reducing the corruption penalty and the final level assembly part count is actually much smaller. The individual tubes are now independent from the overall assembly but dependent on the inseparable weldments which becomes the parent. If all that makes sense.