Allow Application Insights to filter on custom data
Request filtering in Application Insights should allow you to see and filter your custom data on the request sent in the telemetry.
To repo, click a request and see DeveloperMode already in the Custom Data portion of the Request details. Now go to prior blade listing the Requests and click Filter, see that you cannot filter Custom Data properties. This is really unfortunate because I have critical data passed as a custom property via an ITelemetryInitializer implementation that I need to filter by.