Multiplayer Mod Testing

DON'T DOWNLOAD THIS IF YOU'RE NOT A MODDER

Quickstart

Download the mod and run the game
Go to Settings > Mod Options > MultiplayerModTesting > click Enable Testing (no need to restart after changing the config)
Launch a second instance of the game by double clicking the game executable. (If you need to test with a mod profile, you can instead create a shortcut of the executable, see the Executable Shortcut section)
You can connect to yourself with a second instance of the game by hosting a private game with one and opening the console on the other and typing connect localhost:7777
Make sure the config option for testing is set to enabled, either in-game or in the config editor. If using for the first time (and you don't want to reset), tick it to true in Risk of Options in-game for both game instances.

Executable Shortcut

You can create a shortcut that points to the ror2 executable that, when clicked, will open an instance that corresponds to a desired r2modman profile. this is especially useful in scenarios where you need two instances of the game open, such as when testing networking locally.

Steps

Create a shortcut of your Risk of Rain 2 Executable.
Right click the shortcut, select properties.
Open your preferred r2modman profile, go into settings, and select debug, then click Set Launch Parameters
Copy the "Modded" parameters
Back on the shortcut's properties, append the launch parameters into the target field.

step1