What about item sets?

Have you even bothered to read the Ask Riot sections? Or the updates on the new client? Or anything Riot has posted?

Riot says that they are working on adding them to the new client. It will take some time though.

It's not their topmost priority for it but they will bring it back.. hopefully sooner rather than later ;;

work faster! this feature is almost a must! and i never even had them before! as it is i have to have another window open and tab out to remember what item i need to look up. that or actually print something out.... that takes precious time, and im not always dead for 30s when im buying stuff!