My mother she's diebetic patient had her hip dislocation surgery, surgeon splinted her leg so she can't move, underneath splint she has dried up wound covered by yellowish layer on top, is it safe to cover that wound for few weeks as diebetic patient?

Needs exam: What you described requires examination, can't tell if this yellow layer is dried up serum or new infection given that your mother is diabetic. Covering it up to keep it clean is a good thing to do, but you wouldn't know if another infection is starting, kindly ask the healthcare team following your mother for assistance, wish you both wellness