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You could also use my Script Writer program to run your existing AutoLISP program across multiple drawings.

Vijoy, This lisp will work for you. Link: - https://www.cadtutor.net/forum/topic/33301-3d-polyline-intersection/?do=findComment&comment=270303 A great code by David Bethel and enhanced by Lee Mac. Kudos to those two. For it to work it appears that you need to have UCS set to world and be in top view. I tried it on your example drawing and it works. Run the lisp, pick one end of your X-X line then pick the other end of the X-X line. A 3D polyline will be drawn passing through the theoretical intersection points.

Ok a simple trick draw your section line then use trim on your 3d plines the end point will have a 3d value use 3dpoly to join together this is your section. need to do some rotate3d stuff and realign to x axis. Or use the co-ords to draw a new line. Pretty sure there is something about intersect with 3dpoly's around.

First ,Your cross section line must be a 3d poly line with vertex along with elevation, where cross section line intersect with plan 3d poly line must be a vertex.