After selecting the inputs and clicking 'Ok', the send screen will detail the number of inputs and amount that you have selected. You then enter in the destination address in the 'Pay to' field, which can be the same address as they come from. Whatever amount you select which is equal or less than the total amount shown for the number of inputs you have selected, will be drawn from that total. So if you send the exact same amount (less some minor variant usually in the transaction fee), it will send every single input back to the same address as a single input for that amount.

Once you get the number of inputs for that entire address down to a number you can send all at once, your last housekeeping transaction will see you able to consolidate everything down to a single input.


To simplify things, let's imagine you have one wallet with two addresses, but only one of them has a single input for, say 1000BITS. If you perform a basic send, without doing it through coin control, for 900BITS to somebody else's wallet address, it will take the 1000BITS input, deduct the 900BITS and output it to the destination address, while returning the 100BITS change as a new input to the original address.

You could, instead, do a send through coin control from that address and specify that the 100BITS change be sent as an input, not to the originating address, but to your second address. Or anywhere else for that matter, but hopefully it clarifies the function for you.