In a Writer document, create a list. In its properties, make some level (e.g., level 3) to have no numbering. A ready-made sample is attachment 188139 [details]. Now, when inside the list, use "Bullets and Numbering" toolbar, or Format->Lists menu, to increase a paragraph's level in the list. As soon as the level with no numbering is set, the toolbar disappears, and in the menu, the Promote/Demote items get disabled. It looks as if it's impossible to promote the item further. Still, Format->Spacing->Increase/Decrease Indent works, effectively doing the same in this case, as lists' Promote/Demote. But this is not obvious, and it is not clear why a part of list (even without numbering) lacks respective dedicated UI.
I confirm it with Version: 24.2.0.0.alpha0+ (X86_64) / LibreOffice Community Build ID: 77fca616e0bd79e0b405fd0b3543cf8e94e15df3 CPU threads: 4; OS: Windows 10.0 Build 19045; UI render: Skia/Raster; VCL: win Locale: de-DE (de_DE); UI: en-GB Calc: CL threaded Steps: 1. Open attachment 188139 [details] 2. Place cursor in third list-level paragraph Actual result: No Bullets and Numbering toolbar and promote/demote outline level is greyed out in Format -> Lists Expected result Bullets and Numbering toolbar and promote/demote outline level is active in Format -> Lists Additional information: Same result with list styles