If you want to show more than one metric per team, per Heatmap cell, you probably need to create two distinct visualizations: for instance, one per internal and the other one per external.
In your current stack version you have to probably use something like Vega to build a custom heatmap visualization with all the calculation you're looking for.
From Kibana 7.15 you have few more options with the Lens editor, which includes a Heatmap chart type, the filtered metric type and Formulas.
Having the newer Lens version you can do:
- Pick the Heatmap visualization (still experimental)
- on the Horizontal Axis you can put a date histogram, which means drop the "@timestamp" field
- on the Vertical Axis drop the "team.keyword" field, or configure a "Top Values" dimension for the field "team.keyword"
- On the Cell value you could select the Formula tab and type
count(kql="external: false") / count() to check how much work is spent internally
Here's an example using the sample data logs dataset, where I've used a filtered formula:
Does it look like what you are looking for?