cable routing

That depends on the option packages installed on the robot. It also depends on whether your KR240 is a Quantec or not. How are the current cables run? As long as there is sufficient space, you can add additional cables to the existing conduit.

There are option packages that provide connection points at the base of the robot, adjoining the RDC box, which are (usually) connected to a conduit which convey's the user's cabling through Axis 1 up to Axis 2. At that point, depending upon bulk, it may be possible to route an addition conduit up the inside of the A2/A3 casting. Or, alternatively, there are mounting points along the A2/A3 casting for the attachment of external hardpoints.

Cabling running from A3 to the wrist must be run externally, using the hardpoints on the A3/A4 casting.

The option packages are usually referred to by KUKA as "energy supply," and can be researched on KUKA's web site.

It looks like your existing energy supply package is already filled. While you can probably route extra conduits up the outside of the arm between A2 and A4, the root issue will be passing through A1.
On robots that have too much conduit to pass through A1, I usually see people using a sort of semi-circular "cat track" or "cable chain" that wraps partway around the robot base plate, and passes the extra conduit up the outside of A1 to get to the lower A2 mounting point.