If anyone is looking for a gRPC client which will automatically resolve imports between protos and also render structured input fields for each message, check out Protocall (https://protocall.dev - disclaimer, I'm the author).

I built it to solve my biggest pain points with existing tooling like BloomRPC and gRPCurl - they were difficult to use for anything more complicated than "Hello, World". I also couldn't find any tools that would let me send protobuf-encoded requests via HTTP/1.1 rather than gRPC - there are a couple options now, but as far as I know none of them support both that and gRPC.