Scroll Marker Idea
When reading a long article or browsing images with infinite scroll on mobile phone, chances are you see sth you would like to look at -say a link in the article as on the gif above-, but you want to go further first without being distracted and then turn back to it. It would then mean scrolling and scrolling back and forth until you find it or possibly lose.
Similarly when you’re browsing images, there can be sth interesting, but you may want to see more choices before, without opening in new tabs, saving, favoriting etc.
And in case you aren't interested anymore in that link after reading further, or you find better content by browsing further, closing these tabs, removing saved things, unfavoriting etc would just be losing time.
So the idea is, double tap on any point to leave a mark on scroll bar, and tap on that marker to turn there. To remove it, just long press and slide your finger to remove icon.
Markers can be hidden once you begin to scroll -like iOS Safari bar- and appear again when scrolling back.