I am struggling with the same thing. I followed the directions found at
https://blog.mylifeorganized.net/2019/05/using-included-contexts.html but the behavior is not as expected.
I live between 2 different Walmart locations. I want the location based context reminders to go off for any Walmart tasks, no matter which location I end up at. Since I can't have two locations for one context, I have created two contexts, @WalmartThisPlace & @WalmartThatPlace and set up the location notifications. Then I created @Walmart and selected it as an included context for both of those locations. When I switch to "Active by context" view on Android, tasks with the assigned context of @Walmart do not appear under either the @WalmartThisPlace & @WalmartThatPlace contexts.
So then I thought maybe I've mixed up my understanding and have it backwards? So I reversed things, choosing @WalmartThisPlace as an included context of @Walmart, but that also didn't do anything. When I look at @Walmart in "Active by Context" view, none of the tasks with context @WalmartThatPlace appear under @Walmart.
Is this a problem with the "Active by Context" or our understanding of how it works?