a month is probably a bit too long for trays that small. lettuce grows pretty quick and they'll likely outgrow them in 2 weeks or so, but it really depends how you feed them and how much light they receive as this will impact how fast they outgrow the container they're in. most lettuce matures in 40-50 days.. root vegetables shouldn't be transplanted as you'll likely end up with malformed roots which will affect their shape as they grow.

I do plant like Charles Dowding. Wondering what you can plant in a 144 or 288 cell tray? I got them from the greenhouse, since they throw them away every year.

With cells that small, for that length of time, crowding & becoming root bound would quickly become an issue for most vegetables. About the only thing I can think of for those trays would be onion seedlings, since they are slow growing & grow almost straight up.

You can use them for raising plugs but they need potting on pretty quickly. I got some plug plant violas from a nursery and have since then reused the cells for annuals. But they've been potted on after a few weeks. (I grow without heat or lights. If I had them I expect the seedlings would need moving on more quickly.)

Plugs on arrival.... 40 plants per module.

Plugs potted on 18 September.

Starting to pot on further (the ones in front on the ground) 2 October.

microgreens

I know you can hold lettuce for a month, but have never tried kohlrabi and beets in less than 72's. Kohlrabi and beets can be direct seeded in the ground with good success. Another option would be to run your lights 24 hours trading out flats each 12 hours.

I can't really direct seed, since I succession plant extensively. If I had to wait an extra month for seeds to get the size of transplants, I would run out of time at the end of the year for the second crops to mature before freeze. I could try running the lights for 24 hours and swap them out. Didn't think of that!