Here is a simple possibility:

let t := this;
let d := days(Datum, 'Datum Ende') + 1;
for i in range(0, d) do
    create(tablename).
        Datum := t.Datum + i
end;

Line 2: we use the days() command to find the number of days between the two date fields. It doesn't count the starting date so we have to add 1 to the results.

Line 3: then we use the number from line 2, to create a range. We start at zero so we can do line 5 properly.

Line 4: change out tablename to match the table you want to create a record in.

Line 5: we now can use the loop variable to add the correct date to the new record.