I've only seen the release notes, of second beta for version 20.
What's New in Fusion Studio 20 Public Beta 2
• New multi layer tools for Layer Muxer, Layer Remover and Layer Regex.
• New key shortcuts to cycle multi layers with Page Up, Page Down and Home.
I think one is for shuffle of layers around, one is for probably removing and the other might be a way to automate which layers you extract from multi layer source. Based on specified criteria. There is no documentation yet I think so its trial and error and I've not tried it yet myself. Since now all nodes can have layers and these three tools are just added, not sure if more is coming or not. I'll probably wait until more official documentation is out.
Here is some info on the previous beta, or first beta.