May you please rephrase this question, I am sorry but I am not sure I understand what you are asking.
But also, there are other ways to parallelize than what is listed in that documentation. For example, if you are on a cluster, you can use a SLURM job array for example, or even just looping over subjects and putting an & after your dcm2bids command will tell terminal to not wait to start the next dcm2bids command (the downside of that is that you do not explicitly state how many jobs can run at one time, so you have to be careful to have your loop only have as many subjects as you want to run in parallel. There probably is a way to control how many processes go at once, but I do not know the syntax off the top of my head, ChatGPT may be helpful in that regard).
I have one question because im trying to run dcm2bids with GNU parallel for 200 subjects, but it seems to have an error when it is running dcm2bids. It says: catrastophic error: found 3840 but expected 3880 slices. Next, cite the PARREC dir and says error unknown not magnitude, real, imaginary or phase (even the tmp dcm2bids have those files!!), and doesn’t convert the dicom files to bids…but only for some specific subjects, not all of them.
The thing is i have in the subjects folder different files such as: DICOM and PARREC file. Do you think this is the reason for what it is getting an error? Also, do I have to do dcm2bids helper even if there are 200 subjects and im working with GNU parallel?