The variable expansion portion of bitbake could be combined with something like https://pyscript.net/ to build an in-browser playground (similar to https://play.rust-lang.org/) so that users could trivially experiment with bitbake variable expansion and the interactions between OVERRIDES, various operators, and conditional :appends/:prepends. It is key that the actual relevant code from bitbake is used in order to make sure that results are consistent with actual use in recipes.
In my limited free time I have started playing around with an implementation of this using Pyodide and Web Workers. See https://yoctoproject.github.io/bb-datastore-playground/ and https://github.com/yoctoproject/bb-datastore-playground
I finally sat down this past weekend and built a minimum-viable site that is actually useful. Try it out here: https://yoctoproject.github.io/bb-datastore-playground/?code=z%3AIIAgvCBECMkFBwMQgMoAcCmBjAlgQwBsQcA7A0jEABQE8AXACwHsSQBnGkuvADwC4kAATQ0QaAE6k6ACgAmAOgDmGOgDU846ZGCQAlLoQAhcFABM8AMInIAEgDeARQC%2BIe4ZcBmeA%2BsAVeHDAfHhomCSy1iAA7nh08KAA1BCQAPIA0gEIIows0rogdnAgxSAKIWGy6prakAA0UCAAfHgkLDQAtkwArmxi9MysdExMAIQAPFAGTgjIpOQklBxcvCBYLSAMLbIElKSyGFwYEQBGBExYANa9TABmq0z7IENM8IjCojdM4iAAbhrErAA2jV6pBDHUoBZIABdARvEQlYoSKTSG6QOx-cROPgFBTKNQaaSY3ROPRwIA Will be sending an email to mailing list with more details, but I'll also post them here in a separate comment afterwards.