RJ

Additional Car Controls
by Xenolit
Indicators, idle brake lights, door / hood / trunk control, window control, radio skips, slow motion, engine control. interior light control.
Summary
Very reliable and lightweight mod that is very compatible with almost all other scripts. Extremely easy to control your car with just your controller.
Definitely worth the immersion, try it for yourself!  Easy to add or remove at will.
 
Features
Holding the modifier key (X) lets you quickly execute the following:
Control doors, hood and trunk Control windows Skip radio song Control turn signals (signals auto switch off after turning by default) Interior light control Control engine Slow motion Brake lights on idle (brake lights turn on when the car is on and stopped) Menu for more options (control settings, individual controls)  
LSPD:FR & Script engine control
Both LSPD:FR & this script take control of the engine after exiting, you can quickly fix it by doing either:
Press M and go to Vehicle Engine control and put the engine status to on instead of always on OR
Press X + DpadUP (controller) and go to settings, then disable the engine control from there  
Requires
ScriptHookV 1.0.372.2 or higher  
 
Disclaimer:
I did not create nor do I own or edit these files. This script is redistributed by me from gta5-mods website.
If you have any suggestions or direct questions about the functionality of the script itself then contact XENOLIT.
Whether indicators work on custom vehicles is up to the creator of that particular model, auto-idle brakes pretty much always work though.
I've had a lot of requests to make this for keyboards, again this is not my mod, please ask the author but he's been out of reach for a while now.
 
News update: 27/Mar/2019 still works with LSPDFR 0.4