Under front Cushion of Center Console 18'SF??
 

I have attached a pic for Reference. Question is. What was the hatch with the(in my case Blue)Cushion in front of cc Originally used for? Mine is open with a couple battery trays towards the rear of the seat extention. Where they open from factory or was there some sort of drop-in or what? How have others utilized this space?? Pics are most welcome.

I've never seen an insert for this hatch. I've always used the compartment for batteries, life vests, oil reservoir (if 2stk). If I put batteries there I put a hinged partition to keep the batteries separate from life vests or cushions.

I put my batteries up there. Two of them and a Blue Sea Automatic Charge Relay.
Console cover, bimini cover, and usually some flip flops or maybe a towel go in there when we go out for the day.

Ditto