Issue with including external library in own library

Hi, I added an external library (in this case ArduinoBLE, but this is true for all libraries I tested) into my project via the PIO feature, so that it is stored under the .pio folder. Then I registered it under lib_deps.
Now I can include it in a .cpp file and it works fine.

The struggle begins when I try to include the library into my own libraries which are placed in the lib folder. I can include the external library in the .cpp-file of my library and it gets build properly and the dependency graph adds the ArduinoBLE library correctly.
However, I cannot include the ArduinoBLE library in my own .h-file. Then I always get the No such file or directory error.

How can I make the external library available not only for .cpp-files in the lib folder, but also for .h-files?

├── lib
│ └── BLEInterface
│ ------- └── inc
│ ------- └── src

build_flags =
-I lib/BLEInterface/inc

lib_deps =

Manually including the include folder of a library is wrong 99.999% of the time, you should remove it.

Can you change inc to include? This is the standard name of the include folder.

I removed -I lib/BLEInterface/inc and renamed the folder to include and now it is working.
Thank you!