How do I get rid of the D button and switch it back to S for solo

I never saw this D before on a channel. How do I get rid of it?

I went to CoPilot and it said the following

2. Click the “Setup Window Layout” button

It’s the little gear icon in the upper‑right corner of the MixConsole.

3. Enable “Channel Controls”

This is the strip that contains:

  • M (Mute)

  • S (Solo)

  • R (Read automation)

  • W (Write automation)

4. Disable “Channel Racks” if you want

The D (Disable) button lives in the Channel Racks section.
If you turn off Channel Racks, the D button disappears.

I don’t know what channel tracks is nor can I find it. I don’t see it in the Setup Window Layout. I would appreciate if someone could explain how to do this.

Thanks

The D stands for “solo defeat”. You can switch it off by holding the Alt key (Windows) / Opt key (Mac) and clicking the button.

Hold alt or option, depending on operating system, and click on the solo button if you want to engage or disengage solo defeat. It basically functions as a lock button to solo that specific track when you want to solo another track so it doesn’t automatically mute it.