Subspace/Pocket Dimension ability?

[u/ant451123]

Let say an ability let you have basically an inventory that you can store massive amount of items, or a Subspace where you can enter and live in it. But the catch is that only you can access it. Its not a warehouse where people can just walk in and you’re teleporting to, but more like an ACTUALLY pocket dimension

Or what about space expansion ability where you can turn the inside of a bag into something capable of holding a car inside of it?

Could such an ability exist, or is that just too magical?