Can I avoid high cancellation service fee by shortening the stay first?
 

Well, first time Airbnb user, and I know it's probably my fault not to do my dd before using it.

I booked a stay for April and now I might need to cancel. when I booked I saw it was a 'moderate' and could be canceled 5 days prior to the date of arrival, but what I didn't pay attention to was the service fee was not refundable.

In this case, if I submit a change request to the host to shorten the stay to one day, and if it's approved, can I then cancel and be only charged the service fee of one night?

To be honest I don't feel proud of it, but well, my hard-earned money...

it should work in theory, but the host might have a minimum booking policy and might not allow you to shorten it to one day, write a nice note explaining why you need to cancel. April is still ways away so hopefully the host go easy on you.

Another way to avoid the fee is to ask the host to reduce the price to almost nothing, and then cancelling. This would theoretically have the desired effect on the service fee. In this scenario you'd have to explain to the host the whole deal and they'd have to trust you not to keep the reservation.