Hi @CD_Lewis,
Are you using Rhino 8 for Mac?
The Rhino 8 UI has ben unified with Windows UI.
So, unfortunately if you are used to Rhino 5, 6, or 7 Mac now have to get used to this new look.
All the layer controls are unified into the one Layers panel.
See the video that here that shows how to move the column to the left and make it more visible.
Let us know if this works for you.
Sincerely,
Max Fugier
McNeel Technical Support and Training
Seattle, WA