The Stacking Group allows the users to align several elements horizontally or vertically, having no or a predefined fixed space (margin) between the items.
How about a new option, that let the user define a height or width for the group. The contained items are also arranged horizontally or vertically - but in a way that the items are distributed with equal space between them, so that the defined width or height is fully used.
You can do this in a stack group using some basic math. Basically, it is: $[the width or the height that you want]/[the number of items between which you want to distribute the space]$
For example: $(si(rwidth)/2)/5$ or $gv(widthGrp)/gv(ItmAmoun)$
Thank you Leonardo.
However, the calculation will be more complicated if the items do not have the same size.
I think, having a functionality as described originally would be more convenient.