Trimming/patching/surfacing operations with intersecting/aligned polysurfaces/solids

In the above situation, I have used the orange and green objects to trim the yellow one. The yellow one is now an open polysurface, and I need it to be closed (and separate from the other two shapes.)
PlanarSrf doesn’t work because the open end isn’t planar.
Patch can’t resolve all the geometries to seal the end cleanly.
The yellow surface won’t trim a copy of the orange surface (haven’t tried the green one) to create a surface to be joined to the yellow one to close it.
I find that I frequently encounter this problem in intersecting architectonic surfaces where there is alignment (these are all mouldings which intersect where an inside wall corner meets the floor - where all three mouldings’ bottom surfaces are on the same plane.)

Update: I managed to trim copies of the orange and green surfaces by sliding them to more completely intersect, and after doing so with the green surface (the orange one is already trimmed and joined) i got this:

Though the green moulding has slid directly along the yellow one’s axis to be trimmed, when it was slid back into position it shows an extra notch in the above image. This causes a naked microedge error (and an invalid polysurface) when these two surfaces are joined, as shown below:

(Remove All Naked Microedges gets rid of that microedge and the polysurface finally becomes valid and closed.)

But I"m thinking A) there must be an easier and less error-prone way to accomplish this.

Also, B) the procedures I’ve used should have cut an exact cap for the yellow shape – something is causing an error. Maybe a rounding error associated with a maximum resolution for the project, which can be made more fine so that these near-miss situations don’t cause such errors?

The fast way that you use Boolean split and close polysurface with one step, just need have yellow one closed at first.

why not join copies of the green and orange surface and trim that.
But often I encounter naked micro edges too. Which are usually not to be solved logically rather than by trying coincidental retrimming of neighbor surfaces.
Often the open edges move then along the desired body to edges that were closed before. Especially with imported surfaces from ship design software NAPA.

Thanks! Boolean Split. I was forgetting about that.

Glad to know I’m not the only one who gets microedges.