No %Allocation by Month out of the box in Clarity. Best one can do is to put a Time Scaled Value attribute on the Team\Staff page putting Allocation in as the selected attribute and set Display Type to Number. One can use this to allocate hours per month to each team member:
The new resource management screens in New UX allow the same thing, though better – there, one can chose Hours or FTEs, and one has multi-cell copy paste capabilities.
FTEs in New UX is pretty darn close to %Allocation, as one is putting on fractions of a person/role. Screenshot, below, from 15.2.
Numbers entered into new UX fields flow into same TSV fields shown in Classic Team\Staff view.
Does this help?
Dale