Anemones usually only split if they are stressed and don't have stable water conditions. Some do split if they get too big, but that's because of space requirements. Be happy purveyors hasn't split, it means you have stability and that your anemone is truly happy. If you want to propagate and anemone, remove it from your tank, place it on a sheet of glass, with the mouth facing upwards and use a scalpel to cut it in half half through the mouth, you'll have two anemones with each having a part of the mouth. But be warned, you need a steady hand and you cant take your time about it.