In the Outline & Numbering tab of the Paragraph Style window there a controls to define the outline level and the numbering style of a paragraph. This may not work as expected as there are two different concepts of how the numbering for some paragraph works. Therefore the user may need help information at this point.
To see the problem, press F11 to get the Styles and Formatting window, and press the Paragraph Styles button. Right click on some style offered there and choose modify to open the Paragraph Style window. Select the Outline & Numbering tab. You will see somethink as shown in attachment 105322 [details] or attachment 105323 [details] of bug 83071. The controls are disabled if the paragraph is some header style that can be changed using the Tools -> Outline Numbering window. They are enabled for other paragraph styles. The user may want to change the outline style and is not aware that there is something like the Outline Numbering tool. The only thing he or she sees are disabled controls. So how it is possible to change the outline style. On the other hand the user may want to define a header style. He or she sees the controls enabled, selects the outline level and the numbering style and will notice, that this does not work as expected: The outline level will not match the corresponding level in the list style used for numbering. In both cases the user may try to get help using the help button.
What he or she will see is something like attachment 105324 [details] belonging to bug 83071, i.e. no useful information.
You may also have a look at bug 62032 to find someone else who fell into this trap.
The expected behaviour is that there is useful help information which explains that
a) You cannot define Outline Numbering using this window. You have to use the Tools -> Outline Numbering window for that purpose. That is why the controls are disabled.
b) If you define both an outline level and a list style, these things are independent of each other and serve different purposes. The outline level can be used to include this paragraph style in the table of contents in addition to the "standard" header styles. The numbering level that is shown at some paragraph is not controlled by the outline level of the paragraph style (specified in the outline level control above) but set for each paragraph individually using the tab key at the beginning of a line. This works the same way for paragraph styles that define some outline level and those that represent body text.
Observed with LibreOffice version 126.96.36.199 and Windows 7.
Sounds like a reasonable enhancement -> NEW.