A lot of newbies don’t realise it but one of the fundamental rules of UE is that the editor and launcher both use the same engine as the game.
It’s super nice in that your skills in making games transfer smoothly into enhancing the editor or making a launcher. The drawback is that the launcher is the worst part of the whole thing because it’s made using the engine.
Part of the difficulty is that both Slate and UMG need improvements in specific areas. It still boggles the mind that we’re slowly working through more or less the same process as HTML did back in the day. Why don’t we just enable HTML-based UIs? They’re faster, they’re more predictable and you can just access the DOM from blueprints or C++. Expose UE assets to the DOM with a virtual address. Don’t enable any javascript, just CSS and HTML.