Which wallets let you spend partial amounts from your btc address from a cold storage address without the need to import / sweeping it? I know mycellium has the feature, but I'd like to know if there are others that can do this.
I have a "watch only address" of my cold storage in Electrum. In this watch only address I can see all tx, and as such also create tx. I just cannot sign it. So I create it, save it to USB stick, bring it to cold storage, sign it, and bring it back to deliver to the network. I would guess the same can also be done with core wallet.
They all do. Just set your custom change address to the same sending address.
Note: This is a bad idea from a linkability standpoint.