Can I extend a travel voucher this way?

I have a travel voucher from Swiss which is about to run out.

I could use it but wouldn't mind extending it for a bit as I'm more likely to be able to use it for a booking in March (just not set on the dates yet).

Anyway, wondering whether booking a flexible ticket and then canceling it would work? Reading the T&C of the voucher I think it should as I would then get it back in form of another credit voucher but has anyone got any experiance with this?

Also, if a fully flexible ticket on LX fully refundable with no penalties whatsoever?