Hi, Stois. It looks as though you have a tricky numbering issue involved here, which is a bit long to address in a brief post. In essence, you need actual styles for the plain text, underlined bold text, etc. If you are going to number manually, which looks like the simplest approach in this case, you don't need to bother with multilevel lists.

Look up creating Styles. Once you have the several you need, you can simply apply them as needed to you text.

As for the bold/underline following a line of it, you can, when you create a paragraph style, choose what style you would like to follow it. So, assuming you have only one line of bold-underline style, hitting enter will begin a new paragraph in the style you have chosen to follow that one, which could be plain text, or any other.

Best,
Ulodesk