Logging this one, as this has been something that many people have asked about and expected to be possible

Essentially, this is a request to extend the StackPanel StackPanel Element to include a new Property named 'Space between Children'.

This Property would set a Pixel spacing between each first-level Child found within a StackPanel Element.

For context, a somewhat similar mechanic in other frameworks:

In the CSS world, the Property called "Gap": https://css-tricks.com/almanac/properties/g/gap/
(except we would do it across one axis only, depending on whether the Stack Panel was Vertical or Horizontal)

Or in the Avalonia UI Framework, akin to their StackPanel's "Spacing" Property: https://docs.avaloniaui.net/docs/reference/controls/stackpanel