When right-clicking on a gate, there could be a context menu sub-menu (e.g. "Replace with >") that allows a non-unary gate (AND, NAND, OR, etc.) to be turned into another non-unary gate and a unary gate (NOT, Buffer) into another unary gate with the same settings.
When right-clicking on a gate, there could be a context menu sub-menu (e.g. "Replace with >") that allows a non-unary gate (AND, NAND, OR, etc.) to be turned into another non-unary gate and a unary gate (NOT, Buffer) into another unary gate with the same settings.