The phrase "comfortable double sofa bed" means a type of furniture that can function as both a sofa and a bed, and is designed to provide a cozy and pleasant seating or sleeping experience. Full definition
They also feature stylish marble bathrooms and comfortable double sofa beds on the ground floor, which can turn them into triple or quadruple rooms. (travellermade.com)
You find also an elegant and very comfortable double sofa bed (with wooden slats and quality mattress). (romanhomes.com)