When I placed the controls inside a Horizontal Split layout, the controls were not visible. Followed the Configuration options as per documentation.
The Horizontal Split control must be configured with the Pane Specs config options, otherwise it cannot guess how wide or in what way the panes should be displayed. The best way to use this control is to insert a Vertical Layout control for each pane, then use the “Pane Specs” config option to precisely configure how each pane should be displayed.
Horizontal Split Article: https://salientprocess.zendesk.com/hc/en-us/articles/205942258-Horizontal-Split