SA:MP Map Editor

Hotkeys '1' '2' '3' - duplicated object xyz rotation

CTRL + D - duplicate selected object

You can drag & drop an object from panel preview into mapping scene

(Hold)LCTRL + (Click)Left Mouse Button on multiple objects to select them all at once

CTRL + Z / Y - undo

CTRL + S - save 

Delete - delete selected object

W / A / S / /D + LSHIFT - faster camera movement (speed can be adjusted in settings)

Use W / E / R - on selected object to switch between different control gizmos

CTRL + C - CTRL +  V copy / paste object

F8 - scene screenshot (saves on desktop)

F2 - hide UI panels

F11 - Fullscreen mode

Use 'SCENE ENTITIES' to teleport to previously spawned objects around mapping scene

Select any object on the map and use hotkey 'Delete' 

If you have ever used some type of map editor or some game engine well this one works the same expect UI might look different from what you used so there is nothing much to write about or explain all the guide you need for the hotkeys is located in "Help" menu you need max 3 to 5 min to find your way around it...

After app launches you will have to first load you gta sa folder path and click on LOAD button for map scene to appear I'm writing this part because some users could not figure out how to load their map scene although everything was displayed in front of their eyes

Use Settings menu to adjust your objects streaming and other performance demanding stuff although I've tested it on 10y old system with i5 and it gets around 200 fps with default settings and that is with intergraded intel gpu