A temporary work around is to use the _rlnImageName column to grep all the particles in a cryosparc-generated subset from the original input particle star file.
e.g. awk '{print $9}' csparc.star > particles.list to make a list of particle names;
touch csparc_relion.star to make a fresh star file;
Then while read line; do fgrep "$line" all_particles.star; done < particles.list >> csparc_relion.star to grep the particles from the input star and output to another file. (And then add starfile header back).
Obviously this loses orientation information, so will require starting refinement from scratch.
Cheers
Oli