I forget the current chapter that I read in sometimes, and I don't want to re-reading to making a mark.
So, I want a function that I can mark it on my own.
1.) Bookmark it on your browser.
2.) Set the manga to follow. (It will automatically update which chapters you've read/opened since updating it to follow).
3.) Make your own spreadsheet (if you want an example, I can send you one).