I dont see the split command specifically called out in the SDK doc but what you could do is use the LookupcommandID function. Looking at my journal file i noticed that the split command was “ID_Split” so i wrote this quick python script that uses that and looks up the ID then posts that. Now this is just the start you will have to figure out how to get the split point in the correct spot. I have used the postable command a lot in my DynaFabrication2017 package for calling other things in the ribbon such as Snoop.
Just remember that the split function requires you to use the mouse the tell it were to split so the code above will function the same. Now if you want to eliminate the mouse you will have to do something similar to Kulkul approach.