Your wasting your time with Intellij, it’s only really used by some larger gaming companies that can invest time to get it setup well for Haxe. For individuals it will always be painful. Intellij can’t justify investing in good Haxe support so it will only be supported by a few passionate users and never particularly well. Unsure how new this video is, but VSC is the best editor for IDE Haxe users. Obviously some of us are happy to just use a light text code editor and terminal, and a few seem to find Vim support good.
Just use VSC it is the default for most discord Haxe users, so you will always get users that can answer questions, and features will only get better and better. Forget setting up Intellij and spend your time on exploring the haxe ecosystem and games toolkits instead ( heaps, flixel, openfl, nme, ceramic, kha ).