It is possible to share a secret without storing it in a vault first

@gpiepenb

The basic functionality I need is just sending a secret (via an email link) in a secure way

Our item sharing feature will do this. You can choose an item that you have in 1Password, and generate a link to a shared copy of it which you can then send to someone. You can place limits on number of views, time expiry, and email address. There's more information about that here:

☞ Securely share 1Password items with anyone

To share an item with someone, the item must first exist in a vault that you control, even if you delete the item from that vault after you've shared it (the shared copy will still be accessible from that link, depending on the conditions you've set for it).

That way, you can send items to anyone, even if they don't use 1Password, without having to set up guests or create any new vaults.

Give it a try and let me know how it works for you. As an example, here's a test item I've just created, which I've shared as a link:

☞ https://share.1password.com/s#9efFEiZ3Wz1k8u8LDsAqtZc8PmsgnX4wRBq5ZrJ_L3Y

Item sharing links can be revoked before they expire automatically after the timescale you choose.