Is it possible to use static xml metadata for app registration manifest? I know manifest should override policy configuration, and I am trying to use this feature to have single SAML policy, and many b2c SAML clients. I know I can configure static data in the policy, but I need to have it in manifest file. samlMetadataUrl attribute designed for url, not for static data.
No, you can't put XML in the manifest itself. Instead, you would host your metadata file somewhere and point the samlMetadataUrl at that file.
If you truly do just have static metadata then consider hosting the file(s) on Azure Blob Storage either via a public container or a static site.
A word of caution though: this metadata would normally be generated by your service provider, so first ensure there's not some way to link directly to your SP's metadata so B2C can access it in real time.