You can also cook from frozen, which can be handy if one forgets to do an earlier freezer dive. About the only thing you shouldn't do, from frozen is a whole chicken, and mince doesn't work so well, allegedly.
I've only done it once, with a beef casserole. When the cooking time finished, and pressure released, I gave it a good old stir and left it on keep warm for a while.
If you freeze your casserole in whatever portions sizes you find useful, to reheat from frozen, all you need do it put about 100ml water in the inner pot, just to wet it, add the brown iceberg, then set your pot to 15 minutes pressure.
When done, dinner is ready.
I have experimented with the timings on that. For liquidy things, like soup, I have done as little as zero minutes pressure and had double quick, piping hot soup.
For me? This evening's dinner was Mac 'n' cheese for my OH, and Cauli cheese for me.
This morning, I finished off my inaugural batch of home made clotted cream. By finishing off, I mean, I took the cooked cream out of the fridge, breached the top, and poured off the non-clotted element (there's always some liquid when it's done).
My OH was so keen to try it out, he clotted cream on his brekkers. There's decadent!
It was (and is) a triumph.