I also have Styles: Heading1, Heading2, Heading3. Only after creating styles named like that I can make Word detect heading styles and auto create that navigation capable document.
Yes, the Word navigation feature requires “heading 1”, “heading 2” styles to build a list. The best way of doing this in Scrivener is to create those styles in the Styles compile format option pane (close to where you set up Separators), with the look you want in the mock editor below, and then go into each Layout and make sure to assign those styles to the heading in the Section Layouts: Formatting area.
It’s a good idea to check any format you make and ensure styles are assigned to headings in Section Layouts, if you rely upon document navigation. None of our built-in formats assign them by default, but a number are already set up so you easily can (they will have Header 1 set up to match how headings look, etc.).
I understand this is not recommended but for example as I´m outlining my document I´d like to have the ability to insert page breaks at will to remind me of content I would like to write.
Something to consider is that Section Types are not purely level based. If you open the Inspector to the Metadata tab, you’ll find a dropdown that shows the current level-based section type assignment. You can use that to manually assign one instead. What I’m thinking here is that if you have 80% of your content meant to print in a flowing manner from one page to the next, but 20% should have page breaks (for workflow reasons or whatever), then creating a “Working Content” section type that you can manually assign, and then set up with its own Layout that has a page break, might be a better course of action than inserting them manually.
The nice thing about that particular approach, particularly for how it sounds like you are using them, is that marking things meaningfully like that makes it easier to find things like that while you’re working.
Consider for example clicking the Project Search button in the toolbar and typing in, “Working Content”, and clicking the magnifying glass icon, setting the search scope to “Section Type”. Now you have a todo list of areas marked as needing work. But you can even just sort by the Section Type column in the outliner to bring them all to the top.
But in the end, like I say, we have the command to insert them manually for a reason—not everything fits into a logical hole, some pegs are square. If you need, it you should be able to use it. I don’t really know why it’s not working for you. Maybe try RTF instead of DOCX as the file format—both work fine for me in LibreOffice though.