Could I modify metadata value of enableExternalDirectory in runtime

Question

I developed one android app and transform it with ARC welder. So app can run in chrome os.

I add the "enableExternalDirectory": true" in metadata list.

So the app can accessed the file in local storage.

But I do not want the folder selection dialog pop up while first time launching the app.

So, could I disable the enableExternalDirectory in metadata list and enable the value in runtime?

Thanks!!!!!!