Assuming you are in a location subject to the NEC if the wires connected to the breaker that is marked disposal are not connected to anything then you could re-label the wires and use for an additional "small appliance" circuit, but you can't put kitchen receptacle and disposal outlets on the same circuit. To understand the NEC requirements it helps to keep in mind that the Code specifically defines outlet as a point of connection of equipment, and receptacle as a type of outlet.
The NEC requires in 210.11 that two or more 20 amp branch circuits be supplied for small appliances, then later in 210.52 defines what those circuits can and must feed.
NEC 210.52(B)Small Appliances.
(1) Receptacle Outlets Served. In the kitchen, pantry, breakfast room, dining room, or similar area of a dwelling unit, the
two or more 20-ampere small-appliance branch circuits
required by 210.11(C)(1) shall serve all wall and floor receptacle
outlets covered by 210.52(A), all countertop outlets covered
by 210.52(C), and receptacle outlets for refrigeration equipment.
Exception No. 1: In addition to the required receptacles specified by
210.52, switched receptacles supplied from a general-purpose branch circuit as defined in 210.70(A)(1), Exception
No. 1, shall be permitted.
(The above exception pertains to required switched lighting outlet requirements)
Exception No. 2: In addition to the required receptacles specified by
210.52, a receptacle outlet to serve a specific appliance shall be permitted to be supplied from an individual branch circuit
rated 15 amperes or greater.
(2) No Other Outlets. The two or more small-appliance branch circuits specified in 210.52(B)(1) shall have no other outlets.
The critical points in the section are "shall feed all wall and floor" and "no other outlets", so wall and floor receptacle circuits in designated rooms have to be circuited as small appliance circuits, and can't feed an outlet in the cabinet for a disposal, dishwasher, or point of use water heater.
There may be further complications depending on the appliances you are connecting. Disposals often exceed the 210.23 limit of 50% circuit amperage for equipment fastened in place that would allow it to feed other loads not fastened in place.