This post is inspired by a LinkedIn posting from Kris Rice, so kudos to him. Based on that, this post will show how to connect from your Windows host to a VirtualBox VM running Oracle Linux via ssh from the Oracle SQL Developer Extension for VSCode.
First check if the sshd in your VM is running
sudo systemctl status sshd
If you don't already have an ssh key pair on your Windows host, create one via ssh-keygen in the .ssh folder under your home directory
In your Linux VM add the public key from your Windows host by
sudo vi ~oracle/.ssh/authorized_keys
Paste your public key into that file and save it.
Test your connection from the Windows command line.
As you will not be able to choose a username when connecting from VSCode, create an ssh config file on Windows in your .shh folder like this:
Host 192.168.56.11 User "oracle" IdentityFile c:\Users\Arne\.ssh\abruenin-lap
If you don't already have, install the Remote - SSH extension in VSCode
With that extension, you will get the Remote Explorer. It scans your .ssh config file and offers you the ssh hosts that it found.
Click the folder icon next to your connection to 'Connect in New Window...'
In the new server side window, VSCode will recommend you to install the old Oracle Developer Tools for VS Code, though these are marked as deprecated (at least my VSCode did that). Instead install the Oracle SQL Developer Extension for VSCode.
Once installed, you can use SQLDeveloper in the remote ssh window just as you would use it with a direct connection.