Garmin Pilot also shows Pattern Altitude.
It comes from – https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap4_section_3.html
4-3-3 Traffic Patterns, info comes from Chart Supplement. The default is 1,000′ AGL for propeller-driven aircraft.
Some airports do not follow this “guideline”.
I would like to see this info pulled from the Supplement and added.