I want to create an utils folder to create some utils modules. I create it in the folder .\client\your-extensions. It works when I develop my widgets but when I want to export the application the extensions folder is not compiled and the widgets can not import it by relative path.
I import the extension like this :
The solution is modify the html file exported.
Add this line underlined.
And copy the folder extensions from ".\client\dist"
Into the subfolder in the cdn folder in the application exported.
I guess ESRI could create a better way to do that in the futur version of experience builder developer edition.