This style of keyboard is called "40%" and, just as you would press shift+1 to input an exclamation mark, they're invariably set up with additional modifier keys (or chorded sequences) to input the values of all the missing keys.

It's hard to say exactly how this one is configured, because it looks like a custom layout. The kit can be found here: https://5z6p.com/products/plaid-through-hole/

The keys chosen in the primary layout in your link seem much more sensible to me. Trying to imagine what vim is like on the OP's keyboard :)

Small keyboards like this one have programmed layers. You use a key combo to switch between layers, which changes what the keys do.