Timing veg steaming in large steamer.

Don’t you pour boiling water into it?
(Don’t have an electric one, but use hob top steamer quite a lot)

I use a hob steamer too and always use start by pouring boiling water from the kettle into the pan, before the steamers go on the top. Timing starts then, with denser veggies lower down and cauliflower/broccoli in the top. I find it quite easy to just test periodically with the tip of a knife to see if they’re as cooked as I want.
However, sorry OP, I’ve never used an electric steamer.

I find using a big pot of boiling water, cook 1 or 2 minutes and turn off with the lid on gets results.

I've never got the hang of steaming vegetables. Does it really cook them?

I remember some recipes saying to place things on a plate over a pan of boiling water, covered with another plate. I tried it but they weren't cooked at all. Can't remember what I tried that with though, it was so long ago.

I find the electric steamers are brilliant, I've had one for years, and yes, they really do cook the vegetables. You put cold water in the bottom, place the veggies in the plastic basket over the water with the lid on, switch it on, set the timer for say 15 minutes and Bob's yer uncle!

I've decided to cook the Christmas veggies for 20 minutes, possibly less. That should do it. Happy Christmas!

Depends on how you cut them and how you like to eat them. We cut carrots into long batons, about 4 from a medium carrot. They get steamed with the potatoes for about 25 minutes as we like them quite soft.

PS That's after water has started to steam.

I got fed up with the faff of cleaning my 3 tier electric steamer. Now I put my broccoli/cauli in the colander on top of the boiling potatoes and put the lid on top of the colander. Perfect.

I find the electric steamers are brilliant,

I used to have one and it was fine. Sadly one day I left it sitting on the hob while I filled it - over a very hot burner 😲- and melted the bottom of it. Had to open the doors and windows to get rid of the smell and buy new parts for the hob where I couldn't get the plastic off. 🥺 So it was back to the hob steamer, which is fine.