I have a Matlab m-file queuing on HPC, launched using a batch file (non-interactive mode). While is still queuing, is it possible to modify the content of the m-file without the necessity of relaunching the batch file?
If you are using a general purpose HPC that supports Matlab , then yeah.
The HPC is doing something else and it only knows that there is a batch file that needs to run when it has time. The batch file is generally not executed until the time of running the job.
This is true at least for HPC running SLURM (read sbatch documentation)