Missing reference when developing a package in VSCode

Hi all,
I’m developing a package with VSCode so the package environment is activated in VSCode.
The package name is GraphNeuralNetworks.
In order to test some features, I created a test.jl file in the project root folder, so outside of the src/ directory. The question is, why do I get those wiggly yellow lines (missing reference) when writing
using GraphNeuralNetworks since it is supposed to be visible in the environment?