tilly, that sounds lovely: as ummm says all veg are good veg. You can sit things like green or runner beans or shredded cabbage on top as a layer for the last 20 mins and "steam" them without bothering with another pot.
It's a slow cooker pot not a casserole dish. It's made to sit in its casing at the temperature of a low light bulb, certainly not in the oven. If you don't get a loud crack this time, it might well oblige you next time you turn it on in situ.
If you usually thicken stews - I don't, that's personal taste, -just take the lid off for the last 20 mins/ half an hour, and gently reduce the liquid that way.