The files generated by a resin printer slicer contain exposure reference information as well as an image for each layer to be printed. One could consider to develop a reverse-engineering bit of code to read all of the image layers, overlaying the common z-height with the others to be printed and hope that none of them create overlaps that would destroy the models being printed.
One can, for example, configure PrusaSlicer to create a print file, change the name to *.ZIP and extract the multiple *.PNG files within. Consider how difficult it would be to composite these individual PNG files when combining them with another file or multiple files.
The web site 3dprintknowledge contains a beginner's reference with a useful image:
