Thank you, this is very useful. I was not aware of these tools!
In my case, subtomograms are chunks of a semi-regular lattice. The reconstruction allows me to define new subsets of subtomograms in the vicinity, which belong to the same species. So, adding (shifted) particles to an existing species would be a useful feature at least in this project. I went back to the initial extracted subtomos that were refined in relion, and expanded the relion star file, combined, filtered for duplicates etc with relion_star_handler. It then required a little bit of troubleshooting to extract the expanded set of particles (ts_export_particles does not understand fully formatted relion star files; and minimally one needs to remove optics header and add _rlnDetectorPixelSize column, which confusingly must be not the original but the binned pixel size), but it worked very well.
Peter