Hi @fibronic,
WooCommerce already has a built-in feature to leave custom/additional notes on Checkout. When a customer enters extra information the New Order email sent to the administrator will reflect this info next to Note.

Link to image: https://snipboard.io/cgCGj5.jpg
—

Link to image: https://snipboard.io/tKP2vR.jpg
Also, the administrator will receive the New Order email which includes the customer’s billing details such as Name, Last Name, Company, City, etc.
If you want to achieve something different, please be more specific so we can point you in the right direction. Also, sharing screenshots would help us understand your requirement.
Thanks.
Hi Mirko,
Thanks for the reply. What I would like to achieve is create key-value (name-value) pairs that I can use in email notifications. A small example:
Booking Form fields filled in by attendee:
name: Peter
freeField1: I like donuts
zipCode: 1234AB
Email template:
Hi [name],
I see that your zipcode is [zipCode] and that you’ve said: “[freeField1]”.
Another feature we would like to have is custom form input validation, so we can specify exactly, for each field, what the allowed characters are, the maxLength, minLength, regex pattern, etc.
Kind regards,
Frank
@fibronic
This is a fairly complex development topic. I’m going to leave it open for a bit to see if anyone is able to chime in to help you out.
I can also recommend the WooCommerce Developer Resources Portal for resources on developing for WooCommerce.
You can also visit the WooCommerce Facebook group or the #developers channel of the WooCommerce Community Slack. We’re lucky to have a great community of open-source developers for WooCommerce, and many of our developers hang out there, as well.
Hi there,
We’ve not seen any activity on this thread for a while, so I’m marking this thread as resolved.
Hopefully, the above information was helpful. If you have further questions, please feel free to open a new topic.
Cheers.