I just released the next version of the vscode-antlr4 extension, which now supports specifying a custom ANTLR4 jar + own parameters for its invocation. A few bugs have been fixed as well.
As usual you can find the code on Github and the extension in the Visual Code Marketplace.
Strange, but I don’t see it on marketplace in VSCode 1.49.1… 🙁
I was trying to find it under mike-lischke.vscode-antlr4 name
Did you follow the link above? It works for me.