Write automation envelopes with the large rotary (also MIDI mappable) . Popup menus select the device and parameter that you want to automate. There is a third popup which lists the already automated parameters for quick selection too.
All parameter selections are synced with the renoise automation list.
The [+] button adds a new `Instrument Automation Device` in the dsp lane, for the currently selected instrument. If there is already one present then that will become selected, without the a new device being added.