Nelson and Tyler Monroe, I have a passion for the Ingame-Editor, but we need some QOL addons, like possibly an angle measurement system, and just maybe sizing and snapping, because it is a struggle to get the angles right on arches and small decorations. Thank you for your time.
Are you making a domed ceiling or some sort of archway? It’s looking good so far. 
For elaborate designs, I think you might have an easier time creating a custom model (e.g., in Blender). But if you do want to use the level editor, snapping tools already exist. Specify your snap value on the left sidebar. Hold Ctrl while rotating or translating your object to snap. E.g., 15 Snap Rotation will rotate your object 15 degrees at a time.
Was there a more specific feature that you were hoping for?