Microwave/Convection Wire Racks

I leave my racks in all the time. Many of the settings are using both convection and microwave so it is obviously okay to do so. I have never seen a spark like used to happen with older microwaves when metal was inside.

Take the racks out when using MW.

I don't leave the racks in mine when strictly using the microwave function.
However, there is a convection roast function which uses both the oven and the microwave(at 20%) and the instructions specifically state to use the rack. I have done so with no harmful effects to either food or oven about 1/2 a dozen times. But, I have only owned it for a month so far.

On edit: I do not remove the turntable or an part of it when using the only the oven.

You don't mention the brand but, if it's the Sharp CS-930 convection microwave, the answer is yes (use the racks on microwave if that's what the manual says for what you are doing). But this is all fairly new to me, too. We've had this unit for about a year and I'm still referring to the manual. I remember... in the olden days, we didn't put metal of any kind in the microwave... and (for me, anyway) that concept is hard to ignore. So... until you are used to it, refer to the manual often and you should be fine.

Another edit added: Given the other answers that are, apparently, all over the board, I'd say the answer to your question is extremely brand/model specific. For example, the Sharp CS-930 says to use the rack (without removing any other parts) to microwave popcorn.

Remove the glass turntable, plastic rollers, and center sprocket that the glass turntable sits on if using as oven.

Remove wire racks if using as Microwave.

We love ours but need to remember the 2 different configurations. We store wire racks in a drawer under our fridge as we use in microwave mode 75% of the time. Randu

I don't leave the racks in mine.