Export to a multi channel wav file

How can I export my project in a multi line (channel) wav file?

each track for a new wav line/channel.

I tried to add a channel for each track but there are many sounds for some tracks, is anyway to merge it?

Not exactly sure but I guess this is not possible. What you can do is export each track and join them with audacity to multiwav

I tried to stem export. but the MIDI tracks are not available in Channels tab and also I tried to export audio but many files are empty!