See this is what I really don’t understand. First of all, are we talking about listings when you mention “templates”? GS 8+ doesn’t have templates as such any more.
Technically a SKU refers to the specific item (or class of item), not a listing or auction.
If (like me) you only ever have one unique item of any kind (like one book of a given title), then the way to use a SKU is to assign it to that particular unique physical object. If (like many other folks here) you sell commodity things, like shirts or CDs or candy, then the SKU refers to the particular kind of thing, a class.
In the case where they’re unique, then if the item is broken or lost, the SKU should never be re-used. A new unique item is a new SKU, since the inventory amount for every SKU is exactly 1 or 0, forever.
In the case where there is a pool of substitutable commodities, like candy, then the SKU refers to for example “white chocolate KitKat bars, 300g” or whatever, and you associate an inventory amount to that SKU to determine how much remains.
I don’t understand what you’re describing at all. Are you talking about Items in the inventory sense, using the GarageSale Item view? Or Listings (which refer to auctions being prepped or run or completed on eBay)?
And when you mention a group or folder, and “generate a SKU for a group”, what is happening? Are you creating a combination item from multiple items in inventory? Or a listing for many things? Or are you trying to set the SKU values so they all match some other inventory scheme?
I think I just need to have a better sense of what you’re trying to do, is all. I mean, unless you store some kind of extra information in the SKU (which is beyond GS’s ability right now), an absolutely random string would be the best SKU for every item, so they are all always unique. That’s why I use UUID strings for mine.