Dear xax,

May this find you well. I have the Volvo Tech Manual Body Fittings, Exterior (Section 8 ⏞-86, 88]. While it deals with the power windows, it does not deal with the small panel next to the rear window.

Here's what I suggest. Go back to the junkyard. If it is a place where they'll let you remove the part(s) you need, take the following tools:
(a) Metal putty knife (1 1/2" blade and 3" blade).
(b) Plastic putty knife ( as above).

I suspect (but do not know) that the small window is held in place with urethane sealant. If you gently pry up the moldings (and at the junkyard you can find out where to pry and how hard to pry), I believe you'll find that the glass is simply "urethaned" to the metal.

If that's the case, you can then go back to your car, pry up the moldings. You'll need a special sealant release agent (be careful: most solvents will destroy the paint!!!). Once you have the old sealant removed (and it all must be removed, every speck of it), you take a tube of fresh urethane sealant apply a bead to the metal, and bed the new glass into it.

There may be plastic clips, that you'll need to get from the Volvo dealer, which fit on the edge of the glass, into which the molding clips. Alternatively, these clips may be affixed to the metal.

In short, if you can practice on a junkyard car, you can figure out how to do this job. You'll need a sealant remover, a tube of fresh urethane sealant, and possibly some molding clips.

I wish I could give you a step-by-step, but I've never had to do this. The Volvo Tech manual does not deal with this job. Perhaps they assume such repairs will be done by an auto glass specialist.

Yours faitfully,

spook