Connect
From Synfig Studio :: Documentation
Once you have exported your favorite colors, gradients, shapes, etc into the Children Panel, you can reuse them in any layer you like by going to the Children Panel, selecting the value (color, gradient, etc) that you want to reuse, going back to the Params Panel, right clicking the parameter you want to use the exported value for, and picking Connect from the context menu.
You can only Connect to values of the correct type - if you select a shape in the Children Panel and attempt to connect it to a color parameter you will get an error message.
