VIDEO - https://www.youtube.com/watch?v=etkzDbmHe60

Use Alexander Blade's ScripthookV plugin in order to use this.

Press F8 while in-game to open. If you select the controller as your input option via the settings, you may use the controller (Binds being RB+Down) to use the menu.
Otherwise, use the Num keys to navigate.

Spawn objects, peds, and vehicles, and fiddle with them. You've got 690 slots. Have fun.

Update: A crapload of new stuff. EZ Mode, more ped options, spawned vehicle options, funny vehicles, delete all, gravity gun, target into slot, collision, screen filters, time scales, guns, heli rappel, light gun, light creation options, more movement groups and animations, etc. (:

CONTROLS:
NUM2 - UP
NUM8 - DOWN
NUM6 - RIGHT
NUM4 - LEFT
NUM5 - SELECT
NUM0 - BACK

UP - UP
DOWN - DOWN
RIGHT - RIGHT
LEFT - LEFT
A/X - SELECT
B/Circle - BACK