(If your using version 1.0)
Press "H" To Start The Slow-Mo!
Press "J" To To Return To Normal Speed

(If you using version 2.0)
You now can customize your controls

(If your using version 3.0)
You can now input your own speed in game !

Requirements -

Script Hook V
https://www.gta5-hub.com/tools/script-hook-v

ScriptHookV.Net
https://github.com/crosire/scripthookvdotnet/releases

Installation -
Place Slow-Mo.dll in Your Scripts Folder

1.0 -
On\Off Slow Motion

2.0 -
Added custom controls in a .ini file

3.0 -
Added a user input(in-game) for the speed
Enjoy!