Broadly, the idea in Design for Living (first produced in 1933) is similar to that of Private Lives (from three years earlier): people who belong together, or who at any rate deserve each other, try other arrangements before finally ending up together. The difference is that Design for Living involves a triangle plus one—Gilda, Leo, and Otto, plus the longtime friend of all of them, Ernest—so the number of possible wrong combinations for them to try is greater. The triangle wins in the end, and a few of the play's early viewers found that objectionable, even though Noël Coward took care to set it among artists, and notably successful ones at that. Gilda is an interior decorator, Leo is a playwright, Otto is a painter, and even the relatively conventional Ernest is an art dealer; all of them thrive in their careers as the action progresses. A more reasonable objection would've been to ask why the rich and the artistic are allowed to behave differently, but that's a question about the social world of the audience (which Ernest more or less represents), not the world of the play.
I picked up this volume, like the previous one, mainly for tastes of Coward's comedy, so I skipped two of the plays it contains: Cavalcade (1931), a cross between domestic drama and historical epic, which depicts one Mayfair household against the background of 30 years of British history; and Conversation Piece (1934), apparently another operetta in the Viennese style like Bitter-Sweet (1929). Sheridan Morley's introduction gives two intriguing notes about Cavalcade: its premiere production required a cast and crew of 300 people, and the writers of the Upstairs, Downstairs TV series named all that show's chief characters after corresponding personages in Cavalcade. I'm curious to know how it reads, but that'll have to wait.
Three of the nine playlets that made up Tonight at 8:30 (1936) complete the volume. The idea of that series seems pretty remarkable by present-day standards: nine separate one-acts, in various styles, to be presented three at a time, by the same cast, in successive performances. (Tom Stoppard's Coast of Utopia trilogy likewise requires producers and playgoers to ante up for three outings, but even that may have been cheaper than creating sets and costumes for nine different productions.) Contained here are: "Hands Across the Sea," which essentially depicts an impromptu house party that becomes an absolute madhouse; "Still Life," an episodic romantic drama that Coward later expanded into the screenplay for Brief Encounter; and "Fumed Oak," a domestic comedy in which a browbeaten husband reminds us (to borrow Shakespeare's phrasing) that "The smallest worm will turn, being trodden on."