Silicon in e microwave

It's not touching the food and used for a cover..that should be fine for rewarming.

I use plastic wrap to cover glass bowls for lightly steaming broccoli. In your application, it's just a covering for rewarming--that should be fine IMHO.

I bought a silicon lid designed to fit on pots, but I thought I might also be able to use it for covering bowls in the microwave. I use the microwave primarily for heating milk to foam for coffee, but occasionally rewarm soup or other leftovers, so I only use the microwave for short periods. I think you are right: it is probably better to stick to the glass lids.

What type of silicon device. I'd be cautious about it as sometimes the microwave temp can reach higher point than what is on the 'box specs'...and does that very quickly. It would probably be okay for rewarming; which is my microwave oven's primary purpose. But then you get into 'how pure' is the silicon and what additives are used in the manufacturing.
Pure Silicon products from good sources seem to very safe.

Personally, I'd stay with the tried and true classics.