Does "copy-from" and "extend" work on item groups?

#1

Can I use “copy-from” to copy an item group to replace itself, and add another item with “extend” in the process?

#2

Did you try it by yourself?

#3

I found a different solution later to what I wanted to do without copy-from and extend, but since you asked I tried it with copy-from/extend and copy-from/extend do not appear to work on item groups.