As the browser 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.
I don’t know why you’re asking this productivity question on Linux and Firefox communities instead of on productivity communities.
Now I got downvotes in all three productivity communities I posted on:
Are there productivity communities?