While browsing the r/Windows10 subreddit, I remember someone asking if virtual hard disks (VHDs) offered free and additional storage. It gave me a chuckle (if only it worked that way!), but honestly, ...
Use VeraCrypt to create encrypted virtual volumes that mount like drives and vanish when unmounted. Choose a 20+ char passphrase, add key files for 2FA, and generate entropy with random mouse movement ...