Hi,
Unfortunately, the PLU has no that option,
For each LUT input the available input sources are, in sequence:
1. The PLU primary inputs, beginning with plu_inputs(0).
2. The outputs from all of the other LUT elements (aside from LUTn itself) in order from the lowest to highest-numbered remaining LUTs. (For each LUT, the slot associated with the output from LUTn itself is tied low).
3. The four state flip-flops, beginning with state(0).
Have a nice day!
Regards
Soledad