Ask the manufacturer or a suitable installer about approved control options for the exact model. Difficulty operating a button or stopper should not be solved by defeating its function or adding an improvised lever.
What the observation tells you
A control that used to move easily but has become stiff may need repair rather than an accessibility adaptation. Record whether the change is in the accessory or in your ability to use it. Keep any existing protective arrangement intact.
A useful next step
Until an appropriate solution is agreed, have suitable assistance with ordinary operation or use a separate food-waste route. Do not force a stopper or rely on an unattended automatic start.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.