Place custom widget at location in window

[PhilLarkin1]

How might I configure custom widget to appear at a location in the window? None of the position settings are being applied in my app. This is true for the built-in widgets as well. In the image below I am trying to set a custom position of the Legend widget. The widget only ever takes the default position; this setting is ignored. 

[PhilLarkin1]

A better question might be: How might I modify manifest.json to overcome this issue with the builder? Can I hardwire the posiition in the manifest?