How to enter relative (to current page) URL as a menu item?

Question

I would like to be able to enter relative URLs (relative to the current page URL). I've tried the menu type URL (nested within System Links) but when I enter e.g. first it becomes /first and when I enter ./first it yields the same result.

Maybe I've overlooked some functionality?

To give some context and the workaround I've been using:

I have one main menu which resides at / (Joomla installation root, frontend part).

But I also have a menu with 'special' links (navigational links) which appears at a template position only available when displaying a certain component.

So when displaying the other menu, the navigational menu, instead of the main menu, the URL changes to refer to the thing the component needs to display (e.g. /custom-component-prefix/my-very-special-item).

I would like then to have a few relative URL's, so I can then route these relative links (via a HTTP redirect) to display proper follow-up items (and previous items, etc.): e.g. links resulting in: /custom-component-prefix/my-very-special-item/previous (which redirects to previous item) (or /custom-component-prefix/my-very-special-item/next).

Currently I have this workaround: I use placeholders within the navigational menus which I replace with the proper URLs (by means of an override of mod_menu within my template).

Though I would prefer to directly use relative URLs (relative to currently displayed item) which then redirect to proper URL (previous item / next item).

Of course, I could also integrate a custom menu within the component. But then I would have to copy some functionality of the Joomla menu system to that component (Joomla menu system has great support for ordering menu items, changing images and text for menus; so I was thinking about the DRY principle).