Hi Timmypowergamer. Skyboxes are on our to-do list. Can't say when because there's a lot of things we are fixing and adding, but eventually it'll be up there.

List of things we will be adding to the editor (no ETA): sound importer, model importer, texture extractor or direct texture placement on props(decals), text editor for paint mode, skybox control, fog control, object names, light control, room height control, working keypads, recycle bin item, zoom-in feature on static items like in core game, start level with items in inventory, search function, more props.

Some of this things have been added already.

Glad there is a post about this. Skybox was the first thing I searched for when trying to build my first level using a space theme... I ended up pivoting to horror theme with narrow corridors to avoid lack of skyboxes :'D