I am starting to work with welded structures and have encountered a problem. If anyone has a moment to help, I would be grateful.

I made a square structure from an 80x40 profile.
I would like to connect it with a 45-degree bevel.

what operations should I use to add a welded profile fragment while maintaining the bevel below (red), and weld this inclined profile to the plane (green) ?

I tried using the crop/stretch tool, but I lose the bevel.