Are these seedlings "large enough to handle"

No, they are not ready to handle. They still only have the seed leaves. You need to wait until they have a good few of the recognisable Cosmos leaves. Once potted on I always pinch out the growing tips to make the plants bush out. My father used to say that they should not be put outside permanently until after the second week in May, so you have plenty of time.
I love Cosmos, hope you will enjoy them and that they will self seed for years to come.

I would leave them a bit longer and, when you do, hold by a leaf.

However, someone more expert than me may be along in a minute to help.

I wish some of my seeds would germinate! I think they may be duds.

X post from someone who is more of an expert!

Likewise with these sweetcorn - I assume the two outer ones are ok to plant on, but not the middle one, which only came up two days ago - about a week behind the other two

And finally, the cucumbers

Wow - lovely quick replies. Thank you! Sorry to bombard with photos and questions. This is all very new to me.

I'll leave the Cosmos for a bit longer

Same applies to the sweet corn, they need to develope a good root system and true leaves before you disturb them. Only difference is that you don't pinch out the growing tips in this case.

Thank you shysal. I'm learning stuff every day. I think I'm maybe a bit too impatient

Same for the cucumbers as well, you are too keen!
Singly sown seeds in larger pots or cells can be left until plants are large enough to plant out as they won't need to be small enough to separate.

Is that your roasting tin, HurdyGurdy?
What about dinner?

They're all fine in their own pots

Sorry to butt in here.
I’m no gardener but whilst all you lovely green fingered folk are around, can anyone name this gorgeous climber, very popular out here in Spain? It often can be seen cascading over the walls of properties here and I love it.
It’s not scented.

https://www.gransnet.com/uploads/talk/202004/medium-981298-triple-propagator-19-04-20.jpg https://www.gransnet.com/uploads/talk/202004/medium-90451-morning-glory-candy-pink-19-04-20.jpg

Callistemon - No. ha ha ha . Not a roasting tin.

A propagator! A threesome - only one with the lid still on. That one's got the Morning Glory "Candy Pink" in there. Only four of the eight seeds I planted are doing anything yet.

The three pots in the background have melon seeds in there, but I think they're old seeds and aren't showing any signs of life at all yet.

Yes, it does seem I am too impatient - this may explain the limited success I have had in previous years

Oh, the first photo wasn't very clear, sorry

They need two sets of leaves before you move them on

My Cosmos, I’m going to prick them out next week into the troughs that I grow them on in. Not putting them out until frost is over, probably mid May.
When they’re a little bigger, I’ll pinch out the tops so they bush out.

urmstongran, I recognise that climber as one that I had in my garden in Kenya. I think we called it 'flame vine' but it seems that its posh name is pyrostegia venusta.

J52 - thank you for that photograph. Hmmmm, I can see I need to wait a LOT longer before touching them!! That was really helpful, thank you xx

Your welcome, gardening and watching things grow is so special at the moment. Enjoy your plants.

Thank you for replying annodomini
?
Much appreciated!

I kept some of the beans from last year’s runner beans and they are starting to grow! Takes so little to excite me!

My sweet peas look a bit fragile. I am wondering if I should have put more seeds in per pot?

I wish my Dad was here to ask!