Field_group rows

When editing a field_group, even before filling out the empty fields, is it possible that they are not visible but appear only after clicking "add row" (I mean for the 1st row)?
I have another field that updates its value following the number of rows in the field_group but it shows 1 even when the 1st row is empty.
 

No, 1 row must always exist, but such a feature is planned in a future release at some point.

Ok I understand, I will wait then for the future release.
What would you suggest as a workaround in the meantime? Should I condition against empty fields within the field_group?

 

There isn't a workaround available. It's designed entirely to always have 1 row. If 1 row doesn't exist then it will create one at any point in its field processing.

I have another field that updates its value following the number of rows in the field_group but it shows 1 even when the 1st row is empty.

This would probably be where I'd implement some kind of solution. For example check if at least 1 field in row 1 has a value. If none do you could bypass whatever behavior you're doing here.

I had in mind something like if all fields are empty -1 (which will output 0) and if at least one field has a value then do nothing (which will output 1).
This will work even in the case where the 1st row is filled out and the user accidentaly has clicked "add row" and left empty the second one but it will not work in the case where a user has two or more empty rows (three or more in total)! The button allows a user to add as many empty rows as he wants...

You would need to process the JSON then and apply whatever rules you need and count the rows yourself.