If you split your list and then run different marketing (carefully controlling wich variable you change for each campaign) via each part, then you effectively have a form of an A/B Split Test. I thought MailWizz quite good offering the option to split a list in more than just two, as this allows for much more sophisticated testing, i.e. multivariat, not just A/B!
Although I have not done this "split", I assume that it refers to splitting a list. Splitting a list and doing a split test is not the same thing. There is no testing coming with splitting a list.
You can probably do a bit of manual testing, like splitting a list, taking the smaller part and splitting it again and then you have something to test on, but you need to check e.g. open rate manually.
That's what I mean, the splitting is more flexible, but there is no convenient feature to do the whole test (incl stats, randomization, tracking, etc), but at least it does not confine you either (by what often A/B Split Tests only offer in limited features). And hence you can experiment (and that is anyway the whole point of such a test) quite freely and with many variables (subject, content, structure, links, etc).
So, in effect, I hope that MailWizz will keep the splitting feature as it is, even if/when a specific (for most more convenient) additional A/B Split Test feature is introduced