It is possible for a mains powered device (ZigBee router) to use “Source Routing” when sending a ZigBee packet. A Source routed packet includes the entire route the packet should traverse to get from source to destination. However that is done at the packet level by the device. This is usually for very special use cases and the change has to be made in the firmware of the device. The XCTU program is pretty passive it just reads the routing tables of the ZigBee routers. It can’t be used to redefine your routing.
As a side note the SmartThings Hub uses Many-to-One Routing. It periodically broadcast a packet that triggers all ZigBee routers to update their routing table with the most efficient route to the hub. This insures all ZigBee routers have a fresh accurate route to the hub. In my experience SmartThings has nailed the ZigBee routing, my network has been rock solid.
ZigBee end nodes (battery powered devices) don’t do any routing or know anything about the network’s routes. They simply know who their parent is (ZigBee router or coordinator) and connect to it to send and receive data. If they can’t connect to their parent or their parent has orphaned them because they didn’t check in they will have to reconnect. Sometimes if two ZigBee routers are close to the same child it may jump back and forth between the two routers when it reconnects. The trick here is to not make it go through a reconnect process. If it does it usually isn’t a problem your network typology will just change when it moves from one router to another. However, a child device that has to reconnect often will have poor battery life.
I’m curious, why do you want to change your ZigBee routing?