Some servers will kick you for breaking blocks too fast. I sometimes wish to break a block only once every two ticks, for example. This is not currently possible, as filling in "0.1" or "0.5" will automatically set it back to its previous value when you reopen the tab.

vanilla client
options-controls-key binds-gameplay-use item/place block
set to "z"
then hold the "z"

now you have a legal FastRightClickCount, with 1.0 click per tick.

if your server kick you for breaking blocks too fast(1.0 actions per tick), record this and ask the server admin "why tick me, I'm even using vanilla client".