I use MermaidJS for flow chart and Sequence diagram. They have C4 in beta. I tried and it is hard adjust the layout and many features are not supported for C4 yet.
I think you mean Visual Studio _Code_. Completely separate product. Not your fault of course, but the geniuses at Microsoft who gave the same name to two different IDEs in an environment where users of the second one are very unlikely to be aware of the existence of the first. Still, it's an important distinction worth knowing about because they have their own distinct extension ecosystems that are not mutually compatible.
Wow ya learn something new everyday. I had no idea but it did seem odd there were two options from our internal software portal to download ides with similar names but the same exact logo.
for C4 structurizr is the best so far I know. I use that for landscape , container diagrams. I got feedbacks that even CIOs are able to get the picture easy. If they have some ways to produce better layouts for large landscape it would be awesome.
Visual Studio has good support for MermaidJS. https://mermaid.js.org/intro/