The only features that I am missing is in Edit mode: I set out my CHECKLIST to be made up of several logically grouped (and not too long) SECTIONS. Only to find that in the end a given SECTION now became too long, i.e., I created too many items in one section. 

I wished I could split a given SECTION into two SECTIONS.

If Splitting is too difficult to implement, a practical equivalent of 'splitting' would be to duplicate a given section. Once duplicated, I could then rename the SECTIONS and remove items from the original and the copied SECTION, in order to achieve my desired end result.