Plugin window displayed differently in Logic Pro and in MainStage

I wrote an RNBO plugin which essentially works in Logic Pro and in MainStage

In Logic Pro, the two views are

and when in the Editor dropdown Controls is selected

All the numeric UI elements from the presets have sliders and the two windows have the same width.

In MainStage, the initial window looks the same as in Logic Pro

but when Control is selected in the Editor dropdown, the window gets narrower and there are no slider controls.

How can I get the sliders in MainStage?