Mapping a combination of two buttons being pressed at the same time?

I recently set out to map the N64 Duke Nukem so that it’d control like a modern FPS (right stick move forward/backward/strafe, left stick look around). For that Retroarch offers superb mapping tools and I got the job done no muss, no fuss.

Then I set out to do the same for Hexen, but ran into problem of not being able to map strafing since it requires a combination of two N64 controller buttons being pressed at the same time. Can I map such combinations to the remap file through Retroarch or by manually tweaking the remap file?