Which marketing mix element deals specifically with retailing and marketing channel management?

Place.

Explanation:

Place is the part of the marketing mix that is concerned with the channel that is used to deliver goods and services to the customer.

Place determines where marketing happens, what channels the customer then uses to access to product.

For example if a company uses social media to market it's goods, the advertisement directs the customer to the next step which can be to buy directly online, make a call, or visit a physical location.

Then from there the process continues till final purchase.