Reading glTF extras (e.g. from Blender custom properties) to X3D metadata, support changing shape collision mode from Blender, documentation improvements - News - Castle Game Engine Forum
Custom Properties - Scripting for Artists - Blender Studio
Custom Properties — Blender Manual
Read custom properties defined in Blender from scene loaded from GLTF - General Discussion - jMonkeyEngine Hub
I figured out how to use custom properties in shaders and the compositor (Shader AOV). Here's a quick cheat-sheet to get you started. : r/blenderTutorials
Using Custom Properties - Blender 3.0 Tutorial - YouTube
ArtStation - Speed Up Your Workflow with Custom Properties in Blender!