If you didn't know, LGM allows to use your own editors for coding, image editing, background editing, and sound editing.
This isn't issued within the wiki, so I'm making a tutorial here.
To find your external editors, you have to go to "File > Preferences" in the LateralGM menu. There, you'll see a tab called "External Editors".

To set an external editor, you have to make an execution command for it. What do I mean? Well, do you know how does Windows shortcuts work, don't you? They store a "destination" value, more likely a
Windows command, to be executed when you double click them. These
destinations are formatted so they compose of 2 noticeable elements:
- Address. This is what the shortcut points to; whether an application, a webpage, etc... It's always set within quotes.
- Parameters (also called launch options), is a group of specific variables that the adress receives. And is never within quotes.
The "execution command" for external editors work pretty much the same as the shortcuts' destination.
Now you will ask me, "how do I get those destination things?"... I'll do an example for you.
I will be configuring
Paint.NET as my
Sprite Editor.
- Go to the location where the software is located, via your Windows File Explorer. In my case, Hard Drive (C:) > Program Files > Paint.NET.
- Now, click on the address bar. It will turn into an address to that location.

- Copy and paste that address to the external editor field you want to setup. Don't forget to add the quotes.

- Now, add a backslash to that address, and write the full filename of the application you're going to run (obviously, it has to be located inside the folder you just addressed).

- Finally, add a %s to the field, after address outside the quotes. That %s is a parameter. It will force the program to start up AND open a file given by LGM. So, when you click into sprite editing, it will send a temporary file to the program. It's a bit complicated to explain, but I'm trying to make it understandable.

And that's how it's done.
If you have any problems, feel free to ask!