Post old, but quite a few people have a problem with it.
We set everything up in styles, whether we create a new style or modify it.
For me, the requirements were: "1. Chapter title - 16 points, bold, protrusion 1.25 cm" between 1 and the title of the chapter, a distance of 1.25 cm, space after the title at 14 points. I created a new style. After the name we have a style type, there I chose: Combined (paragraph and sign). Then I set what I had and set the rest using the Format button. Then I went to Paragraph. There, in the indentation tab and the spacing at the indentations, I gave 0 cm and for the special ones I chose the extension option and there I gave every 1.25 cm. Below I set the spacing after (by entering the appropriate value, I have 14 points). Sometimes you need to set the spacing before instead of after

After accepting it, I chose Format again and clicked Numbering here. There I chose the appropriate option (you can always define your own) - it is important to set dots after subsections, because it is often forgotten.
The same problem appeared as with the author of the post.
I clicked on a multi-level list, then chose the option with headers, where the list looks like this:
1. Headline 1
1.1 Headline 2
1.1.1 Header 3
e.t.c.
Of course, my styles were called differently, so I clicked again on the multilevel list and there I gave Define a new multilevel list (it defined me on the basis of this list above). Thanks to this, it was enough to click on the number on the left (from 1 to 9) and there on the right, next to the Assign style to level option, choose your own style (I don't remember if I did not develop something in this window). It's almost done. There was a problem that the ejection blew me away. So now for each style for the chapter (I had 3) I gave modify and then Format further Paragraph and there I changed these spacing (how to change is described above). By selecting this list it made me different spaces. After these changes, everything is fine for me.
I am uploading my file to prove it works

maybe it will help someone.