You say here you can get a glowing effect using the "World Environment node" and a "HDR modulate color". But how do you do this? In the example file there is no world environment node so I'm not sure what to change if I add the node. Also when modulating the colour of the circle, the Red value is at 351 in the example but I can't make it any higher than 255 for mine.
The way you would do this is, in your level's scene, you would create a WorldEnvironment node and assign a new environment resource to it. When you expand that resource you can activate the glow post-processing effect.
As for setting modulate colors to higher numbers than the initial limit, when using the color picker, look for a toggle button named Raw.
When turned on, this setting lifts the cap for color values and allows you to select HDR colors.