YouTube Keyboard Shortcuts: like/dislike, backup/restore position, change speed, picture-in-picture

This script adds keyboard shortcuts to perform common actions on YouTube without clicking or exiting a full-screen video.

Shortcuts on regular video player

• [ to like a video
• ] to dislike a video
• b to save the current playback time, meaning the script will remember your current position in the video
• r to restore the saved playback time, jumping back to the moment when you pressed b
• h to enable or disable Picture-in-picture mode, creating a floating video that keeps playing even if you switch to another application
• } (Same as Shift + ]) to increase playback speed by 5% (so going from 1x to 1.05x to 1.1x… etc. as you press multiple times)
• { (Same as Shift + [) to decrease playback speed by 5%
• x to go forward by 5 seconds
• z to go back by 5 seconds
• shift + x to go forward by 1 second
• shift + z to go back by 1 second
• u to "undo" a time jump and go back to where you were just playing (e.g. you pressed "0" by accident, press "u" to go back to where you were)

Shortcuts on "YouTube Shorts" video player

• all of the above, plus:
• k to switch between playing and paused
• l to go forward by 10 seconds
• j to go back by 10 seconds
• , (comma) to go back by one frame
• . (dot/period) to go forward by one frame
• 0, 1 … 9 to go to 0%, 10% … 90% of the video
• f for full screen (this has limited utility since the top and bottom of the video will likely be cut off, maybe try w first)
• w to switch to the "classic" YouTube player for this video, instead of staying on the "Shorts" player with a feed (w as in using the "wide" player)
• shift + w to switch to the "classic" video player, but open it in a new tab to avoid losing the current "Shorts" feed

The shortcuts listed from k to 0..9 are already built into the regular YouTube player, but did not work on the Shorts player; this script makes them available for Shorts.

Other features

• Discreet notifications are displayed when you use these shortcuts, so you can tell what happened even if you're watching in full screen.
• Notifications can be disabled by changing a single line featured prominently at the top of the code.
• How long notifications stay up (2 seconds by default) can be changed in the code, it's easy to find (search for NOTIFICATION_DURATION_MILLIS).
• The script tries to remove the built-in notification that says "Feedback shared with the creator", although you can disable this (search for REMOVE_FEEDBACK_SHARED_WITH_CREATOR).
• The speed change for { and } can be configured in the code as well; it's 5% by default but the constant can be updated in a single place (search for PLAYBACK_RATE_STEP).