Bump. I know the fix looks a bit ugly but it makes a big difference to the UX of adding recipients

Should this PR be targetting 4.0 (CMS 5 compatible) or 3 (CMS 4 compatible)? I don't think there's any breaking changes here, so I would have thought 3?

userforms relies on the LeftAndMain.currentPage session value to find the form ... That obviously doesn’t work for userform elements

Just to make sure I'm understanding this correctly - I'm assuming this doesn't work because the currentPage value is set to the actual page (or other object) which owns the elemental area rather than to the userform block edit form?

It would probably be worth adding a comment to the top of the new method explaining that this is a workaround for that session mismatching - that way if we ever change LeftAndMain.currentPage to respect GridField item edit forms (which IMO would be a more correct fix for this) we can come back and revert this change.

Just to make sure I'm understanding this correctly - I'm assuming this doesn't work because the currentPage value is set to the actual page (or other object) which owns the elemental area rather than to the userform block edit form?

Yep exactly

I’ve rebased this now and targeted 3. I’ve also added some more descriptive comments explaining why this code exists

Can you please provide step-by-step instructions for reproducing the original problem from a fresh installation? I can't seem to reproduce it with this module in the 3 branch.

I think to recreate it you need to set:

SilverStripe\UserForms\Model\Recipient\EmailRecipient:
  allow_unbound_recipient_fields: true

If you then create a form that has at least one field with the Email type, then when you add a new email recipient against a (elemental) userform, you’ll see the “Before” screenshot above which includes the message:

You will be able to select from valid form fields after saving this record.

To select from the list of email fields defined in the form, you have to enter an email and save it first, then you’ll see the dropdown with a list of fields to choose from.

After this change, you’ll see the “After” screenshot where you can immediately select an email address from the list of user defined fields before writing for the first time.

Can you please provide step by step instructions? I'm unable to get the "before" screenshot even with that configuration. I only ever get "after".

Maybe relevant, here's the versions of things I have installed when I can't reproduce the original problem:
dnadesign/silverstripe-elemental 4.10.0
dnadesign/silverstripe-elemental-userforms 3.x-dev f51cd57
silverstripe/admin 1.x-dev 304a4d2
silverstripe/cms 4.x-dev 9269356
silverstripe/framework 4.x-dev 1f7adab
silverstripe/frameworktest 0.4.12
silverstripe/session-manager 1.x-dev 75dd7e1
silverstripe/userforms 5.14.0
symbiote/silverstripe-gridfieldextensions 3.5.0

My bad, my framework version was locked to 4.11... turns out another genius has already fixed this in framework 😉 silverstripe/silverstripe-framework#10297