inserting a section to a heterogeneous part

Hi all, a question about inserting a section.

I would like to insert a section between two sections of an existing heterogenous part.

e.g, insert a section U?B between two existing sections U?A and U?B.

how shall I go with this? Currently I change the number of section in the Option but the new section will only append at the end of the part.

Thanks in advance.