Yes. You can add several cost lines to the contract, each on its own production code. We still recommend one production code per contract when possible.
How to do it
Open the contract in Purchasing for editing.
Click Add under the cost lines under Costs.
Choose Status, Production code and Cost for the line.
Repeat for each production code the contract should be split across, and save.
Good to know
One production code per contract gives more accurate follow-up, because costs and invoices then belong in one place.
The opposite works fine too: several purchases or contracts can sit on the same production code.
Check that the sum of the cost lines matches the contract value.