In Writer, Insert - Caption (press F1 or Help button). Notice that "Numbering separator" appears in Insert Caption dialog, but not on help page for Caption ( https://help.libreoffice.org/7.6/en-US/text/swriter/01/04060100.html )
The help page is this one: https://help.libreoffice.org/7.6/en-US/text/swriter/01/04060000.html?System=UNIX&DbPAR=WRITER&HID=modules/swriter/ui/insertcaption/box1#bm_@@nowidget@@ (You linked to the one for the Caption Options dialog) Do you know when this Numbering Separator is available to use? I see it always greyed out.
(In reply to Stéphane Guillou (stragu) from comment #1) > The help page is this one: Thanks for correction. So let's expand this ticket to include missing "Caption Order" on Options page for Caption. > Do you know when this Numbering Separator is available to use? Use Options dialog to set Caption Order to "Numbering first"
https://gerrit.libreoffice.org/c/help/+/146208 should take care of the issues raised here (and also clarify how to activate "Numbering Separator"). Also, have changed the position of "Caption" on the Insert Caption help page to correspond to the order of the dialog.
Seth Chaiklin committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/7266a58cba3c89fdf9cd7100c00ef360e8d45e08 tdf#153122: Add missing controls to Caption and Caption Options help
The patch in comment 4 adds the missing items to the Insert Caption and Caption Options help pages. This resolves the OP, so closing close this ticket as FIXED. Meanwhile, problems with existing entries in these pages are now reported as bug 153551 and bug 153552.