CdRMoteer The basics are explained here: https://wiki.cosmoteer.net/index.php/Moddinglanet_Editor
Note that there is a right-click menu for many UI elements. Save often as some things will crash the editor, like >=30 octaves of perlin noise (the most I ever actually used was 10-11) or using a color channel as alpha multiplier (I crashed the editor with this most often).
There are regular spherical layers and "halos" as used by the "star" planet. The spherical layers work by creating perlin noise (check the internet for information) based on parameters you enter and then colorizing it with a color palette you define. You can set the position of each color within the band (which automatically reorders the list as needed) and its transparency. If you want harsh steps instead of smooth transitions to the next color, that's what the "segments" parameter is for.
To make one layer add to the previous one without completely overwriting it you can give some colors transparency by lowering their alpha value. This is a situation where you might want to use segments=1 to have an instant transition from fully transparent (showing the layer below) to fully opaque. The vanilla lava planet has one layer of red lava and one layer of gray stone with transparency pretty much like that.
You can chose how much a layer is affected by self shadowing at the bottom ("darkness"). For glowing surfaces like lava or the sun you can set it to 0 and go to Material-Target Blend Mode where you would set the destination RGB multiplier to 1. This part might be a bit confusing at first. Blend Mode defines how your current layer and what is already on screen will be mixed together to form the next output. Destination is what is already on screen, source is your current layer. At the top you define the output color and at the bottom the output alpha. Note that alpha is invisible since your screen can't turn itself translucent, hehe. You will be able to see it if you take a screenshot though as it will save to a transparent PNG.
The basic blending goes like this: OPERATION(source source_factor, destination destination_factor). For the operation we have a+b, a-b, b-a, max, min and for the factors we have 0, 1, source/destination color/alpha and their inverse. Do not pick a color channel as factor for alpha or the editor will crash. Other than that feel free to experiment. A destination color factor of 1 will result in additive (glow) blending. The settings for alpha are mostly uninteresting - since invisible - until you want to use "destination alpha" from the previous layer for some advanced effects. Just be sure that in the final layer, the alpha value is 1 everywhere or you will have transparent screenshots of your planets. Also inside the Material settings is a color setting that has an interesting aspect: You can set values over 255 here to enhance the contrast of color or alpha channel as I have done for the alpha channels of the supernova above. 2 halos and a sphere are used to create an interesting alpha channel as base for another sphere that contains the nebula texture.
Further down in each layer you'll find number ranges that you can use to randomize the rotation speed or colors of your layers. The radius works a bit unintuitively for halos, since there you have an outer and inner width which are both subtracted from the radius.
I haven't worked much with halos yet, but it seems that how thick the halo is, is directly proportional to its alpha value at that point in the texture and that only one pixel row of the texture is shown at any time with the animation moving that row through the texture. Halo textures must be repeatable in both directions, unlike spherical textures.