I am working on a SLURM-based cluster, and I'd like to know if there exists a command (or a configuration file to look at) I could run as a user to know the maximum number of jobs I am allowed to run simultaneously (I did not find it in the Slurm documentation). Is there such a command ?
The resource limit you should look into is MaxJobs.
As explained in the docs, it can be set in several ways. Per user association, per account (group of users), per cluster. Also, set directly by asociation or via the quality of service (QOS).
You should first check which account(s) is(are) associated with your user, e.g. with sacctmgr list user $USER.
Then, you can check MaxJobs with sacctmgr list associations. Look at both your account (near the top of the list) and your user.
Finally, check the values set with the QOS with sacctmgr show qos (look for MaxJobsPU and MaxJobsPA, per user and per account IIRC).