I know what you mean as I've seen extension strips for Schuko outlets, and the ones for French plugs which are almost the same (just the reversed pin for ground instead of the side contacts).
We can get 3-way "cube" adapters for our 13A British plugs. One of those with a full complement of three 13A plugs is huge!
That's one reason why I still like to use the older 5A round-pin plugs in my workshop. They're much smaller and neater, and ideal where you have a lot of low power equipment.
