The phrase "additional layer of complexity" means that something has become more difficult or complicated because another aspect or factor has been added. Full definition
The gameplay has never felt this tight, and the new mechanics add additional layers of complexity to the combat while still being accessible to new players. (wegotthiscovered.com)
All relationships face tough times, but same - sex couples deal with additional layers of complexity. (couples-counseling-now.com)
Bernard Hickin continues: «The use of Scotch whisky barrels to finish our Double Barrel Shiraz has imparted additional layers of complexity and smoothness, which combine beautifully with the rich varietal plum, fruit cake and chocolate notes of Barossa Shiraz. (thedrinksreport.com)