[mat]

I'm working with a document that has a number sequence like

2.
2.1
2.2
2.2.1
2.2.2
3.
3.1
etc

In between the numbers are text images paragraphs etc.

I know how to add a new entry in the middle of a simple sequence of
numbers but I'm not sure how to insert a new number in the middle of a
complex sequence like this? Mostly I'm not sure how to insert a new
number like 2.2.3 in the sequence after say a paragraph or two of text.