Over the past couple years, people have started using various cool techniques on code.org's gamelab, especially with key values to create chat apps and other multiplayer projects. It may surprise you, but most of these techniques were pioneered by me. For example:

setKeyValue/getKeyValue on gamelab: I did this in 2019 to create game where you can share drawings to people in gamelab
Remix detection: I discovered both methods, keyValues and getURLParams()
encodeURIComponent() for sanitizing userid's in keys: Ziriski actually took this from me in discord.

It may surprise you even more to know that there are way more of the aforementioned "techniques" that you may not know about, all contained in one single document. There are:

IP logging methods for gamelab and applab
Server networking capabilities for gamelab and applab
3d rendering with textures and shaders

Document in question.

Here are some multiplayer games I made that most people have forgotten. All of them are secure against hacking. Heroku server will take time to warm up.
online maze
connect 4 multiplayer

That's not it. By taking advantage of code.org's API's, some projects have been created to accelerate code.org game development.
Data browser allows you to edit the key values of a game lab project and the records of an app lab project.
CDO-Sync Allows multiple people to collaborate on one project at the same time as well as full on typescript support.
CDO Monaco Cdo-sync, lacks multi user, but has typescript and is very convenient to use.

Note, a lot of techniques on applab no longer work anymore. This is because code.org removed heroku as a valid domain for web requests. It is still theoretically possible to use records for web requests instead, but it is too much effort for me currently.