Okay. I see what’s happening. I think this is an understanding thing.
The defined mode for each layer (or tabs as you call them) are not pre-canned. Also, except for those layers that are saved into the design, each layer will retain the last used set of parameters. Every layer can be customized so you can change between line, fill, or offset fill.
Multi is not an option that you select. It automatically will display if you have opened up the cut settings by double-clicking the layer in the Cut / Layers window. If you have multiple sub-layers defined there the main Cut / Layers window will show multi.
You can add more sublayers by pushing the plus button in the cut setting.
LightBurn has created a video that explains sublayers:
How To Use Sub-Layers In LightBurn - YouTube