See the deep dive on desktop prefs for more information
We were looking to run an experiment in v115 that required setting a pref. We have registered the pref and landed it on beta, but uplifting to release so late may be problematic. Is there any way to make this experiment work in 115 without that update to FeatureManifest.yaml landing?
No, the only way to set prefs currently requires them to be registered in the feature manifest.