To split coin blocks, you need to enable the coin control features (wallet > settings > options > display > display coin control features). Then select one block at a time, and send it to yourself, adding your (same) address as the 'custom change address'.

So say you start by selecting a 1000 XQN block. You then send yourself a transaction of 500 XQN, but specifying the change address as your own as well. Once you hit send, you will be splitting that 1000 XQN block into 2x 500, a primary transaction, plus change, back to your original address.