Progress Telerik UI for WinUI
The Telerik WinUI GridSplitter allows you to redistribute the space between columns or rows of a Grid easily. By simply dragging the splitter, the targeted columns or rows will be resized. The control automatically detects the targeted columns/rows to resize, while dragging. You can also manually specify the Resize Direction Auto, Column, Row and the Resize Behavior to select which columns/rows you'd like to resize.
Check out the Telerik WinUI GridSplitter documentation for more info on how to get started with the control