magit-todos VS git-link

This is not an exact solution you are looking for, but magit-todos displays todos in magit-status buffers. If your repository is huge, this can slow down magit, so I don't know if you would use it.

This is an idea I've been thinking about for a while, since Bufler reached a point of stability, to use structs to define hierarchies that can be filled with objects automatically. It finally came together in my mind and this is the result (still WIP, but it's working well). I expect to use this in Bufler, org-ql, and some other projects. It could be useful as a "backend" for magit-section, ewoc, etc, similar to how magit-todos uses hierarchical magit-sections (taxy would offer a cleaner, more flexible grouping backend).

Take a look at magit-todos, IIRC it works asynchronously.

git-link package. It supports a good number of online git hosting services. It also integrates with git-timemachine package, and can provide a link to a specific version of a file.

I heard about this project recently; it does not open the webrowser directly, but it puts URLs for the forge in the kill ring, including line numbers: https://github.com/sshaw/git-link

Another problem is jumping to a particular place in the code, e.g., I want to open a link to the specific line in the current (or some other) branch that's hosted on GitHub. How do I do that? You can use git-link.el and browse-at-remote.el. They have some similarities and overlap in features, but they do have differences as well.