Stacked bar chart for Total Values in Trends Insight

Feature request

Is your feature request related to a problem?

I want to make a stacked bar chart in the Trends insight that has the following:

• X-axis: Breakdown of source property
• Y-axis (the stacked bars): Breakdown of query_source_kind property
• Value: Total insight creates

This would let me visualize the distribution of insight types by source. Currently, I cannot do this in Trends and have to resort to a Custom SQL insight.

When I use multiple breakdowns in a bar chart, this is the closest I can get:

Describe the solution you'd like

Looking for something like this:

I could also see us having a "Breakdown" insight as its own insight type. This could include all static charts (without a time series):

• Table
• Bar chart (horizontal + vertical)
• Pivot table / heat map: https://github.com/PostHog/posthog/issues/20251
• Stacked bar chart (this issue)
• World map

Describe alternatives you've considered

I can use the SQL editor to build this chart, but it feels like it should be possible as a trend

Additional context

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]

The issue does not name files, tests, or entry points. Start by locating the Trends insight implementation and its existing multiple-breakdown bar-chart handling, then trace how chart configuration reaches the UI. Done means Trends can display total insight counts with source on the x-axis and query_source_kind as stacked segments, with coverage for the new configuration.