As Firefox is by far my most used app, I find that bookmarking the current tab and describing the task with no more than a few words or even as little as a few chars, to be a good way to keep track of what things I need to do soon. For things I would get to later or whenever I feel like it, I’ll put them in Firefox’s “Boookmarks Menu” or “Other Bookmarks” folders, and have lots of folders consisting of Reddit posts and searches about different topics.
If you like playing with Bookmarks then i strongly recommend Tab Stash extension, I used to use it from the side bar, but when I discovered it can be opened as a tab, it’s has become the first tab I open in every session
So to answer your question, yes I do use Bookmarks as a To do Tomorrow, To view later, To Researcher in the future… Etc