Hi, in the vMix blog, the following was described:

"vMix now supports the ability to receive multiple tracks of audio which will be combined automatically and made available to the input’s channel matrix and mixer. On the output side, support has been added to split the single multi-channel track into multiple stereo audio tracks."

This was under the heading "SRT Updates For Audio and Replay", but I'm hoping this also applies to playback of ProRes video files with embedded multichannel audio. I recently had an issue where the downmix from 5.1 ended up being a mono mix of just the LR channels, so we had none of the dialogue in the playback...which was a problem. Hoping that the v26 update allows for more flexibility when dealing with embedded multichannel audio mixes, fingers crossed!