Hi nos, yeah it's a selection filter - when it's activated only things that match that active filter will be targeted for selection actions.

So for instance if you want to select all red curves, you can tag Style = Red with a filter, and then go to the Types section of the scene browser and click on the selection indicator for curves and it will only target curves that have style = red. Or you could do a window selection and only things with style = red would be selected inside of the window.

It can help with doing more specifically targeted selections.

You can push Escape to clear any active filters when you are done using them.

- Michael