XYplorer treats space as a part of search keywords, so QuickLook does not override it. However, it is possible to set a custom hotkey to invoke QuickLook.

To do that go in the User > Manage Commands... menu. Select Open With, then click New.... Set the caption of your choice, then set the path to QuickLook.exe, surrounded by double quotes and followed by "<curitem>". You can assign a hotkey by clicking on the Assign Keyboard Shortcut button: