I have two parts in a document, the first is a documentation, the second an appendix.

Right now, I have follwoing structure:

1. Headline 1
1.1 Headline 2
2. Headline 1
3. Headline 1
1. Headline 1 (This shall be the appendix, I restarted the numbering)
1.1 Headline 2

Now I want to add a prefix, A, before the Appendix headline, so that I get this structure:

1. Headline 1
2. Headline 1
3. Headline 1
A1. Headline 1
A1.1 Headline 2

I know that I can define such a thing via Bullet and Numbering, yet there the appendix is defined for all the headlines. But I only want it for the actual appendix.

How do I achieve such a thing?