Booking multi leg return to Japan using voucher

[Gothbe]

I’m trying to book from BHD-LHR-HND-KMI return with no stop overs on the way out but with a 2 night stop in Tokyo on the way back and use a voucher.

Without the stop over the website brings up the flight options without issue. I’ve tried using the multi city option, putting in the 6 flights, but it shows no results. However, if I use multi city it does return results for bhd-lhr-Hnd-kmi and kmi-Hnd-lhr-bhd when run separately.

Am I missing something that I need to do?
I’ve tried ringing BA and the agent was particularly unhelpful saying that if the website doesn’t return a result he cant do it and allow me to use a voucher.

[NorthernLass]

Are you trying to book this as a return with a 241 voucher? I may not be understanding what you’re trying to do exactly, but when you search for a return reward flight you can only input your start and end points and are stuck with whichever routings ba.com throws up.
You should be able to select each leg separately though, and you can change the date at that point.

[Gothbe]

My apologies, I should have made it clear that it’s BA evouchers that I’m trying to use. The issue I’m having is factoring in a stopover after the first flight on the way home