Hi @marci080, you are welcome!
Actually, if you check a Date/Time component on the form, the Data tab offers customisation and once in the past, I have used it to customise my input using Flatpickr options.
The Time Formatting Tokens section on this Flatpickr page does offer the seconds option but it’s not working for me on the picker dialog itself. I have to edit the text instead of just typing in the popup.
Hopefully this will offer some light to your research and get you what you need.