Unable to edit custom fields

Since last update of A+ I was able to edit custom fileds in the appointment admin screen.

Now the custom fields appear greyed and I cannot edit them.

This is vital for my business as I have custom fields like surname or vat number, which must me editable.

Can you let me know how to make them editable again ?

Please also read my previous post on this argument a few years ago. Since than everything worked up to now.