This Ableton Live walkthrough shows two ways to build layered instrument sounds inside an Instrument Rack: dragging a new instrument straight into the chain list, or using the Create Chain command from the context menu to set up an empty slot first. Either method lets you stack multiple instruments under one set of Macro controls.
From there, the video covers mapping more than one parameter to a single Macro. Filter frequency and Time both get assigned to Macro 1, first through the Map button and then through the right click context menu, so one knob now controls two parameters at once.
The Mapping Browser is where the real control happens. It lets you set a custom range for each mapped parameter, useful when a full sweep is too extreme, like narrowing filter frequency to move between 300 Hz and 2000 Hz instead of the full spectrum. You can also invert a parameter's min and max values from the context menu, so turning a Macro up can push one parameter higher while pulling another lower.}, giving you finer, more musical control over layered sounds with a single gesture.