You can now hold Q in order to drop items rapidly. This bug can be easily reproduced if you are holding a stack of items. This was not an issue in 1.12.2.
Sometimes, you can also press ESC in order to rapidly pause and resume the game.
Linked issues
Comments
I do not know if it can be reproduced on 1.12...
Good noon!
Cannot be reproduced in 1.12.2, can confirm in 1.13-pre5!
@GamerMan12, comment confirmed.
I created a MC-132395 in the morning

Duplicate of MC-118107.
Please use the search function next time.
i heard when you change the right click button to a different key, you will rapidly fire items so quick same time when you drop items. (such as snowballs, xp bottles, eggs, anything else you can right click repeatedly) this only works when you stand still, moving around while holding the key will be in a normal state.