POS never create a new address for the involved coins

if u send coins in a transaction the change will be placed in a new address if u didnt specify ur address as change address
(option in gui for one session or option in diamond.conf for be used permanent)

if u read my answer before again it explain u dont need to combine coins by utilize coin control

if u still want to use this "expert user tool" it can be expected u know what u do