Creating discontinued paragraph number + Indexing (Law)

Hello everybody,

I'm writting to you because I need assistance about a complex layout ..

In some books (Treaty, biology, law etc.) the numbering of the paragraphs is discontinuous (with marginal numbering). This system, which consist in a number of steps, is designed to allow for the integration of new measures and the creation of new ones.

Here is a typical example:

I wrote some remarks in red to better understand this concept.

I only managed to do a paragraph numbering with paragraph styles (Normal style) with a green caracter style like:

100

101

102

etc.

I also managed to make anchorages text, but without the possibility of "selecting" the numbering, as in the example.

To conclude, if this formatting is possible, would it be possible to make an index with the style of paragraphs providing its marginal notes numbered?

I'm looking forward to hearing from you,

Pierre