Did you try to use Cope? or use a reference Plane to cut?
YOUTUBE | BIM | COMPUTATIONAL DESIGN | PARAMETRIC DESIGN | GENERATIVE DESIGN | VISUAL PROGRAMMING
If you find this reply helpful kindly hit the LIKE BUTTON and if applicable please ACCEPT AS SOLUTION
Following Forum discussion might be helpful to solve your question!
https://forums.autodesk.com/t5/revit-structure-forum/miter-joint-in-timber-beams/m-p/10486104#M44451
Cope Webs to Chords and zero out the Coping Distance.
thank you. forgot about that command.
thanks.