Perhaps this is not supported but here is my scenario.
I created a workspace and multiple applications using Sencha Cmd v184.108.40.206
I wanted to reference Ext outside of my workspace directory because of source code repository issues and noticed that "workspace_directory/.sencha/workspace/sencha.cfg" has a configuration for ext.dir. I changed the default value to a different directory outside of the workspace.
The sencha app build completes successfully but I noticed when I load the app, the Ext framework images are missing
The following directory isn't being created in the build folder: