sites -
https://editor.appybuilder.com
https://ide.niotron.com
Extensions mostly use Java. There are sites like GeeksForGeeks, StackoverFlow etc. from which you can learn how to make extensions.
I want IDE's
I use intelliJ idea mainly
If you don't want to configure your PC you can use
https://ide.niotron.com/
I am already using niotron IDE. Any other ?
Not working
Don't have a VPN
Well try with a different browser maybe then.
Still the same thing.
I guess your question is answered. The rest is up to you.
Now I'm using VS Code. I used to use a notebook.
VSCode for me is just a java editor. I am using Git to compile the finished java file.
As @Patryk_F said VS Code is just s IDE (place) to create "Java" files you can write any java file you want.
and use Git bash or cmd to compile it with ant
or rush
see @Aquib_Khan ide just help you edit your file and appybuilder and niotron is a ide because you type in it and change your code and to compile you need ant that will generate your aix