Export extendable bin as one piece

[yawkat]

With an extendable bin like this: https://gridfinity-extended.ostat.com/gridfinity_basic_cup#eyJleHRlbnNpb25feF9lbmFibGVkIjoiZnJvbnQifQ%3D%3D

Right now, you have to select the front or back part of the bin and export them individually. It would be useful to have an option to include both parts in the export, separated by a gap so that you can just "split to objects" in the slicer.

[ostat]

This would require calling the main function twice.
I think we would need to make a new file for that use case.