Thank you for your question, and apologies for the delayed reply.
Merging two geometries is often a challenging task, especially when dealing with complex setups like the one you have already implemented. Unfortunately, there is no fully straightforward solution, but I can outline the approach I would take.
First, I would define an RPP in the TH_TP2 region using the envelope dimensions of the tray6 geometry. This RPP should then be rotated to the final position required for tray6. Once correctly positioned, subtract this RPP from the TH_TP2 region to create a placeholder. You will encounter a geometry error at this stage, but this is expected and intentional.
Next, prepare the tray6 geometry in its own input file, ensuring that it is already placed in the correct position relative to the minister_concept6 geometry. This geometry should be enclosed within an RPP having exactly the same dimensions as the placeholder RPP created in the first file.
Finally, copy and paste the tray6 geometry into the minister_concept6 input file. If everything is aligned properly, this should work relatively smoothly. In principle, you will then have two identical RPPs at the same position with the same name, of which one of them can be removed once all zone and region names have been properly adapted. Make sure to carefully check for any remaining hidden geometry errors.
I hope this explanation helps. Please feel free to come back if anything remains unclear.