Be nice to have the time and energy.
Eggshells are mainly Calcium carbonate, basically chalk. Cannot see how it would do anything much in the way of fertilier, except to keep the compost a little more alakline.

lack of calcium causes blossom end rot, so perhaps it is to counter that. But a decent tom feed will be easier.
my egg sheels get crushed and go round the hostas. Slugs don't realise they are not meant to slither over the shells.

One of my uncles lived near to a factory which used thousands of eggs. He used to get the shells from them and added them in massive bulk to his very clay soil. It was cheaper than buying limestone and it did improve the soil no end.

And I’ve been saving eggshells for ages, they must be useful somewhere.

I have a container of crushed egg shells, I use them around plants but have found the pesky slugs & snails still get to munch in the leaves Grrr!
I'll have a go at putting them round the tomato's this year :o)) x

All my eggshells have been added to my compost bins for years, I don't bother to put them in the oven, I crush them if I remember, often they go in as they are, they break up gradually as I'm turning the compost a job I do regularly, I also found the snails and slugs ignore the sharp edges and slither over them, it amuses me when something that even my grandfather always did is considered the latest new tip....

Its just to prevent blossom end rot. Its much easier to crush part of a stick of white chalk instead. Cured mine in no time.

I put my egg shells in my wormery. Worms love them! It sounds like a lot of work to do for a bit of Alcalinity though.

We crush our shells and add them to the compost bin. Is this called recycling?

Well, I guess eggs are still cheaper than oysters! :)