Solution
There are two ways to resize controls using splitters in LabWindows either manually or programmatically.
A) Using Attach/Detach Control Dialog Box
Controls can be attached or detached to the splitter using Attach/Detach Controls dialog box. This dialog box can be accessed when splitter is double-clicked and press
Attach/Detach Controls.. button.

B) Using AddCtrlToSplitter function
Controls can be
programmatically attached to the splitter using the AddCtrlToSplitter function and configure the attachment mode.