Ive been fiddling around with the item editor and have managed to get a grip of it to some extent, but im not sure what to do about blocks automatically putting themselves in different Groups whenever you copy paste sometimes etc(becomes problematic when trying to move around the desired stuff/ add faces etc).

Also, is it Worth using the item editor or is it better to pick up and learn a 3d program like blender for example?

You can sort your items manually in:
Documents\ManiaPlanet\Items\

You can make your own folder, and they'll show up in-game after a restart.

It's definitely worth learning the item editor & mesh modeler. Although currently there are some things you can do with Blender+ the NadeoImporter that you can't do with the in-game editors.

Any idea what causes the editor to crash? happens sometimes and last time it did, i saved my item 3 times by clicking the save button( though without exiting the editing interface), which apparently left me from where i began when i loaded up the game again after the crash.

Also, is it possible to make perfectly smooth Square grid spheres instead of trianglular spheres either through the editor or by importing a model? i tried it with the editor and my methods did not work as i could not snap the things properly(partially because i suck at it lol).
Wondering this because triangular geometry is apparently bumpier than Square geometry in some cases. btw, i have no idea why some of the standard blocks are over 5k+ polygons and faces when they look so simple, like the 1x2 upward Concrete blocks. i get that it makes them ultra smooth but i Think 1-2k is well enough in some instances.