That folder lives in Benjamin's home directory, so it's not created "at login" — it always exists on disk. It's just not accessible to other users because of standard Linux permissions (/home/benjamin_loison is readable only by its owner). You don't need to log in as that user; you need elevated rights or a permission change.

Option 1: Temporary access with sudo (recommended)

From any admin account on the machine:

sudo ls "/home/benjamin_loison/VirtualBox VMs/"
sudo cp "/home/benjamin_loison/VirtualBox VMs/somevm.vdi" /somewhere/writable/

Or open a root file manager session (Cinnamon):

sudo nemo "/home/benjamin_loison/VirtualBox VMs/"

Option 2: Grant permanent access via group membership

If another user needs regular access:

sudo usermod -a -G benjamin_loison otheruser
sudo chmod g+rX /home/benjamin_loison        # allow group to traverse the home dir
sudo chmod -R g+rX "/home/benjamin_loison/VirtualBox VMs"

The other user then logs out/in and can read the folder.

Option 3: ACL (finer-grained, no group juggling)

sudo apt install acl
sudo setfacl -R -m u:otheruser:rx "/home/benjamin_loison/VirtualBox VMs"
sudo setfacl -m u:otheruser:x /home/benjamin_loison   # traversal only, home stays private

Notes

• Moving VMs out of the home dir (e.g. to /opt/vms or an external drive) is often cleaner if they're shared between users — VirtualBox lets you change the default machine folder in File → Preferences → General.
• If the concern is instead that you want to run the VMs as a different user, be aware VMs are registered per-user in ~/.config/VirtualBox; copying just the .vdi/.vbox files is fine, but permissions on them must also allow the new user to read/write (chmod/setfacl accordingly).
• Never chmod -R 777 a home directory — it's unnecessary and insecure.

If you meant something different (e.g. the folder doesn't exist until login because of a mounted/encrypted home), let me know — with an unencrypted ext4 install the folder is always there, but with ecryptfs encrypted home directories you'd need sudo ecryptfs-recover-private /home/benjamin_loison to mount it without logging in.