When you split a booking, there’s just one rule to remember:
You can only split the second part of a booking — the first part is locked.
Example:
You book 10–20 Aug. You split it into:
10–15 Aug (first part — can’t be split again)
15–20 Aug (second part — still splittable)
Now you decide you want 13–15 Aug instead. Here’s the trick:
Change the first part to 10–13 Aug.
Change the second part to 13–20 Aug.
Split the second part into:
13–15 Aug (your new dates)
15–20 Aug (what’s left)