In order to prevent loops (WF A calling WF B calling WF A again), we added an artificial blocker for IWF chains with more than one level of depth.
However, I think there was some effort on its way to allow your scenario. Not sure, whether the work has already been completed.
For sure, you can try it out. It either already works or the programmatic safeguard is still in place and you will get a respective error message.
Thanks for your quick answers.
It indeed is not possible, but I think a feature that would (together with allowing the same integrated-WF used multiple times in a master) highly help to build really modular workflow chains (like when calling functions inside other functions in any programming language).