[feature request] top/bottom & left/double-midle/right offcuting lines in split pages

[mrelg]

For the "fill offcut" function to be meaningfully useful (while not using "fill margins'), instead of the current one-or-two, offcutting/splitting lines "split pages" should have four (for single) or six to eight lines (for double pages).

Not all of them need to be (but can if developers find it feasible) automatically located but should be available for manual adjustments.

In the single-page variant of the "split pages" dialogue, lines should enable cropping the page from top and bottom as well as currently available left and right.

In the double-page variant of the "split pages" dialogue, the current centre-splitting line should be doubled or thickened to allow the removal of a black band in the middle while "filling the offcut"
Like in a single-page case, there should exist left and right lines to enable at least manual removal of page edges.
Another two, but preferably four lines should enable (at least manually) cropping the two pages from top and bottom.