I noticed that custom environment var defined in the Start build > Advanced section did not override the ones that was defined in the App Env Vars.
For example, I have a default App Env Var for $FOO containing value “bar”.
When I start a build using Advanced section, I added custom environment variable for"FOO", with the value “baz”.
The result is when reading FOO, the predefined value (i.e. “bar”) is always read.