Companies from banks to tech giants are looking to shed huge chunks of office space. Here's a look at 8 key sublease offers — and what they mean for rents in big-city markets.

· Tenants such as Airbnb, Yelp, Allianz, and Macy's are tossing big blocks of sublease space on the office market.
· That's threatening to flood supply at a moment when the commercial real-estate market is already struggling in the wake of the Covid-19 crisis. 
· By adding to supply, sublease inventory pushes down office...