YouTube Double Tap Scroller 作者： Ivan

Double tap on the left central side of the video to rewind 10 sec and double tap on right central side to fast forward 10 sec.
This works only for tapping. Double click on left and right sides will run fullscreen.
This add-on is only for youtube.com.
Developed for touch-screen laptops or tablets.
*Supports mobile app.
*Supports other sites, which contain youtube iframe (to use this addon in fullscreen in the mobile app, you now have to use custom player controls).
*In Options is possible to set up rewind/fast forward interval (1sec - 20sec) and the tapping area's Width (10% - 50%) and Height (10% - 90%)

Now (March 17th, 2020) www.youtube.com and m.youtube.com have their own double tap scrolling, so you can turn off my scrolling in the options page.
The add-on is still helpful with youtube iframe on other sites.