Simulplay Button Not Showing Up

Hello! I am trying to set up the audio for my campaign but the simulplay feature that is noted in the wiki is not showing up for me. In its place is a shuffle button instead. I have loaded on Edge, Chrome, and Opera and they all show the same button options. Is there something I am missing or is this a subscription only feature that isnt listed on the subscription perks?

It's a bit confusing, but it is there (for me),  It's only showing on a Playlist. Does not show up on an individual track.  It's 1 button that you keep pressing and it cycles through the options. The button shows a different symbol depending which mode option it's on.  You may need to recognize the button differently depending on which mode it's already on now.  The button is just to the right of the tringular Play button.  The button and its appearance cycles through (1) one-play, Loop button, Shuffle button, and last comes the Multiplay button you're looking for.  When you cycle that button to look like 3-lines with arrows, that's the Multiplay (simulplay, simultaneous) mode. 

Ahhhhhh ok gotcha. I guess the info I was seeing from forum posts before on like "how-to" guides were outdated. Thank you!