Hello Bwildly, I took a look through the manual for the A110L and found the same section you likely read:
"In dehumidifying mode, the appliance should be prepared in the
same way as for air conditioning, with the air exhaust hose attached
to enable the moisture to be discharged outside."
To be honest, most of our portable air conditioners with a dehumidify mode tell you not to vent the hose outside when the intention is to dehumidify and not cool. With a unit like the A110L the auto evaporative function makes this infective though.
I'm thinking that venting to your sink won't help much because the air coming out of the unit should be humid but not humid enough to condensate on the sink and drain.
Is there any other way to vent the unit? Perhaps a vent or opening in the basement wall?
You could always get a dedicated dehumidifier, they tend to be quite a bit better at removing moisture from the air than portable AC's and there's no venting to worry about.