For a visual tool I'd recommend giving IcePanel [0] a try.

For the diagrams as code solution, happily it looks like mermaid will soon support C4 [1] so their should be native support in lots of places soon (github, gitlab and lots more have built in support for mermaid)

[0] https://icepanel.io/

[1] https://mermaid-js.github.io/mermaid/#/c4c