Hey Daniel, on modifying the spans - certainly possible since you can actually just do px.launch_app(trace=px.TraceDataset(df))
However augmenting Traces is a bit of an an anti-pattern for telemetry data as it's meant to be a runtime artifact. We probably will not support direct modification of spans from a technical standpoint.
There are a few options that are actually tracing compliant for adding custom attributes to the spans themselves at runtime.
We probably will support "human" annotations on spans just the way we support "ai" evaluations on the spans but these will be implemented as annotations in addition to the spans. Does this match your use-case? What labels would you like to add to your spans? The above solution might solve them.
I hear ya on wanting to show and pin specific attributes on the table. Good feature ask! I filed a ticket - please upvote if this makes sense and let us know what some of your use-cases may be! https://github.com/Arize-ai/phoenix/issues/2236
