Hello,
I'm using a Mac mini with not enough space and I wanted to know if it's possible to keep my normal user but create a new one where I can download for example Xcode and all the Xcode data is in my external drive.
Sure. In System Preferences > Users & Groups, control click or right click on the new account and choose "Advanced". From there, you can change the home directory.
Make sure to first copy the home directory to the external drive. I strongly suggest using the "ditto" command to make sure all of the ownership and permissions are correct. You also might want to do "Get Info" in the Finder on the external volume and make sure "Ignore Permissions on this Volume" is off.
This is the closest Apple Support document that describes the procedure: Change the name of your macOS user account and home folder - Apple Support. It isn't quite the same though.
Sure. In System Preferences > Users & Groups, control click or right click on the new account and choose "Advanced". From there, you can change the home directory.
Make sure to first copy the home directory to the external drive. I strongly suggest using the "ditto" command to make sure all of the ownership and permissions are correct. You also might want to do "Get Info" in the Finder on the external volume and make sure "Ignore Permissions on this Volume" is off.
This is the closest Apple Support document that describes the procedure: Change the name of your macOS user account and home folder - Apple Support. It isn't quite the same though.
Make sure to have a good backup before you make any changes. Also read very carefully the Apple article @etresoft linked as you must perform those steps exactly in addition to the copying step mentioned by @etresoft. Many users tend to miss a step.
Is it possible to create a new macOS user and change its home directory to external SSD
