Hi Ingo,
Thanks for reaching out.
There's no way to insert a custom field's value into a URL directly — SP Page Builder doesn't support placeholders inside the link field, so .../form?name={field} won't work. Apologies for the inconvenience.
What does work is storing the finished link in the collection itself. Add a Link type field to your collection (Dynamic Content → your collection → Edit → Custom Fields), enter the complete URL with parameters per item, e.g. https://your-site.com/request-form?name=Team%20A&email=team%40example.com, then select the Dynamic Text addon acting as your button, open Link, enable Enable Dynamic Link, and pick that field under Link Field Source. The query string is passed through to the target page exactly as entered.
Please also note that our Form Builder addon has no default value option, so it won't read those parameters by itself — that needs a form solution that supports pre-filling from the URL.
Best regards,