There is no button for it. The window is worked out rather than negotiated, so nothing in the app will add days.
Two things are worth knowing before you conclude you are too late.
Your window may be longer than the store's policy
If the item was damaged, faulty, wrong or not as described, you get the longer of 7 days and whatever the store's own window is. The store cannot set a shorter one for this.
So a store advertising "no returns" or "3 days" has not shortened your window for a faulty item. That is the single most useful thing on this page.
A change of mind is different: there you have only the store's window, and a store is entitled to offer none.
Which means the first question is why
Not "how long have I got" but what is wrong with it. If the answer is "it is not what the listing said", the clock you are worried about may not be the clock that applies. How returns work
The store can agree anyway
A store can accept a return it is not required to accept. Many do, because a returned item resold beats a bad review.
Ask directly and early. "It arrived while I was away — can I send it back this week?" gets a yes more often than people expect, and far more often than the same message sent a fortnight later.
What does not work is going quiet and hoping. How to message a store
If you are simply undecided
The window is short for a reason: both of you need the question settled while the item is still as it arrived.
So the useful move is to open the item and look properly on the day it comes. Most late returns are not people changing their mind on day nine; they are people who did not unwrap it until day eight.
What does not extend it
Being away. Understandable, not a mechanism.
The parcel sitting with a neighbour.
Waiting for somebody else's opinion. Raise it first, decide after — opening the conversation is what stops the clock mattering.
If the window has genuinely passed
For a change of mind, that is usually the end of it.
For something faulty that you could not have seen, say so and ask. A store refusing where the item was misdescribed is a case Metzee will hear. If you are not happy with our answer
More: how returns work, do I need the original box, who pays return shipping.