How do we use the new (v7.2) page style parameter "gutter"

With v7.2 page styles have a new “gutter” parameter. When adjusting the setting for one of my mirrored page styles. Are we talking about the gutter for the binding? this would be on the left on one page and the right of the next. Or are we talking about the gutter between two columns?
Since the Writer manual for 7.2 isn’t out yet some of this is unclear

Have you tried to press Help at the bottom of the tab in the page style dialog? Usually built-in help is up-to-date compared to the manual.

Since 7.2 is not yet officially released, it is still considered experimental. I have not had a chance to experiment with it yet. In typography vocabulary, gutter is a space between two columns. The parameter would set such a space. However, in my 7.1.5.2, the Columns tab offers the possibility to set the gutters individually. So, I don’t see the use of this gutter parameter.

From Help 7.2:

Gutter

Enter the amount of space to leave between the left edge of the page and the left margin. If you are using the Mirrored page layout, enter the amount of space to leave between the inner page margin and the inner edge of the page.

not tested by me.


See also:

Given the definition returned by built-in help, I don’t see the improvement over the inner/outer margin definition when in mirrored mode. It might be only a cosmetic change, unless this applies to all page style “modes”. But in this case, what about “Only left”? Does it still modify the left side of the page or does it apply to the right side which is supposed to be the inner side?

7.2.0 was released on Thursday, Aug-19, download here.

From the current online help:

Gutter
Enter the amount of space to leave between the left edge of the page and the left margin. If you are using the Mirrored page layout, enter the amount of space to leave between the inner page margin and the inner edge of the page.

It’s odd that it is available as an option with Right and Left pages. In that case it does what it says, add to the left of every page making for very odd looking layout. However if you have flip pages (bound at top) then it might have some use when Gutter position is set to Top
For Mirrored pages, it takes space for the inner margin. It just makes it a little bit easier to size the gutter without having to do any minor calculations