You can modify a window's properties by right clicking on that window in the tree and selecting "Set Properties...". A dialog is displayed allowing you to set a number of properties including window styles. Note that not all properties can be modified.

The "Set Properties" dialog

Below is a list of window properties that can be modified:

Text Sets the window or control's text.
Dimensions/Pos/Size Sets the position and/or size of the window or control. In pixels where 0,0 is the top-left corner of the screen.
Visible Whether the window is visible or not.
Enabled Whether the window is enabled or not.
Always on top If the window should remain on top of any other windows, even when it does not have focus.

Within this dialog, you can also set window styles.