Created attachment 166503 [details]
Instructions and text document for demonstrating problem
File > Send > Outline to Clipboard and Navigator - Headings - (context menu) - Send Outline to Clipboard
Both use the same function, inherited from OOo
Attached document gives test document, with instructions. Basically, the idea is to use that function to copy and paste an outline. The test document and STR should help you to see that "Outline Level" information is lost when pasting to another document.
Given that there is no documentation on this point, then you can decide whether this is a bug or an enhancement.
In fact, clipboard RTF is all affected by that, not only when using Outline to Clipboard function.
Select All -> Ctrl+C -> in a new document, use Paste Special to choose RTF.
OTOH, saving the document as RTF and re-opening keeps the outline level -> there is a way to store necessary information in the RTF.
The data copied to clipboard has outlinelevelN attribute. It is ignored when pasting. The same happens if pasting RTF copied from, e.g., Word.