Borderless Fullscreen
Multiple Monitors Support
Hotkey Toggle

How to install it

Download RuneLite from their website: https://runelite.net
Launch RuneLite
Click the Wrench icon on the top right of the RuneLite window
Click the Plugin-Hub button on the right side near the top
Search for "Borderless Fullscreen"
Click Install

Demo

Borderless.Fullscreen.Multitasking.mp4

Borderless.Fullscreen.Multiple.Monitors.mp4