The MediaBay button to “Include Folders and Subfolders” is not working correctly in Cubase 13 for me. These 4 screenshots show the issue.
In this one the Include Folders and Subfolder Button is disabled and the MediaBay is correctly showing the contents of the selected Folder (also verified using Windows Explorer).
Now the same Folder is selected but the Include Button is enabled, and it shows no items in the same Folder.
Now lets look at the Parent Folder. Here it is with the Include Button disabled and correctly showing only the files in the Parent Folder.
Finally the same Folder with the Include Button enabled shows no files in that entire Folder Tree which actually has tons of files.