I was a C++ Chrome developer till 2020, and I primarily used Sublime Text because of speed, and I found VSCode weekly releases too distracting.
I indexed code locally with CTags, and then used SublimeText CTags extension for navigation. This worked great for my local branches. When I needed to dig deep, I'd use source.chromium.org which indexes perfectly.
I am not sure if built-in indexing supports only indexing subset of the tree. YOu want to selectively index for speed and accuracy. The complete tree might contain multiple definitions of the same functions, as headers get copied, pre-processed, etc.
It supports selective indexing, you can specify paths to exclude from indexing or you might open just a single module, here is more info: https://www.sublimetext.com/docs/indexing.html
I indexed code locally with CTags, and then used SublimeText CTags extension for navigation. This worked great for my local branches. When I needed to dig deep, I'd use source.chromium.org which indexes perfectly.
# ctags command that indexes just Google's chrome code ctags --languages=C++ --exclude=third_party --exclude=.git --exclude=build --exclude=out --exclude=tools --exclude=mojo --exclude=base -R -f .tmp_tags ctags --languages=C++ -a -R -f .tmp_tags third_party/blink mv .tmp_tags .tags