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What I want most is "jump to definition". Maybe not as full fledged as the true IDE, but just ctags like behavior is immensely helpful.

The Sourcegraph Chrome extension provides this for Python, JavaScript and a few other languages I think.

I known. But their language support is very limited.

I've made codesearch.xyz with that purpose. It lets you enter repo URL and then it lets you search and browse the code.