OP_CHECKWILDCARDSIGVERIFY or "Wildcard Inputs" or "Coalescing Transactions"

addresses the problem of small UTXOs and high transaction fees has been proposed. The issue arises when multiple small donations are made into a single address, resulting in a large number of UTXOs that have to be listed individually during transactions. This leads to higher transaction fees. To solve this, a new opcode called OP_CHECKWILDCARDSIGVERIFY is proposed. This opcode evaluates true only if the signature is a "wildcard signature", which is a signature created to express the private key owner's intent to make the input a wildcard input. A wildcard input ignores the value of the input, unlike regular inputs, which respect the amount. A coalescing transaction combines all the UTXOs with a matching locking script and creates a single output with the total value of all the inputs. This transaction also includes a wildcard input signed with the new opcode. The wildcard input ensures that all the UTXOs are combined into a single output. As a result, the transaction fee is reduced since there is only one input. While this proposal still needs some refinement, it could be helpful in solving the problem of small UTXOs and high transaction fees.