The supported way is to write a script which uses REST to pull a list of SVMs and then pull a list of files per SVM. If you enable filesystem analytics, you can use the REST API to download a list (see page 22 of this PDF - https://www.netapp.com/media/20707-tr-4867.pdf)
You could also use XCP in scan mode to output a list (https://library.netapp.com/ecm/ecm_download_file/ECMLP2875795)
.. but the easiest way is to unlock the diag user, login to systemshell and then "cd /clus", run "ls -lR" or whatever option you want and redirect it into a text file somewhere inside the heirarchy of /clus/svmname/volumename - Systemshell should not be used except where absolutely necessary. Be sure you understand how to run the commands listed, and redirect output to a text file and the potential consequences if it breaks. If you have any concerns, please use one of the other two methods.