This was actually what I want to avoid. The lfo/gainer and also the signalfolower methods.
Especially for the coming UPDATE of Renoise I would really prefer better Sidechaining.
The Thing is that renoise already can send Midi impuls to Instruments and also that VST3 will NOT be implement in the next Update as we now know. Vst2 and sidechaining works somehow but also seems more complicated inside renoise and thats why we havent got that Feature.
What I also did find out is a Way to Sidechain via Midi-Triggers inside the current Renoise - Version and it somehow works (not perfect yet it for now doeas the work):
The Plugin you need for this Method is called Duck by Devius Maschines (they have a demo) - Then apply the following Track one needs a VSTi with a short trigger or drumsounds (doesnt matter which as you can mute the Audio) on Track two you put the Duck vst as fx PLUS FX Alias and set the SC Trigger to MIDI on that vst (alias fx) - on Track three you then put a pad sound or bass (This will be Sidechained by the Duck fx) ALSO the Duck vst hat to be put on the Track three as a normal FX (in the Mixer) AND you also have to send the Midi-data from Track one (instrument 1) to the Track/Instrument 2 (fx alias Duck vst) to make this work. You will then see the Midi input blinking inside the Duck vst which the INPUT there you also have to set from Audio to Midi (trigger) at the right bottom of the Duck VST; It is a bit complicated to setup but it works like a charm you can trust me on this and thank me later.
Track / instrument 1 = vsti with short trigger sound (routed to track/ins 2)
Track / instrument 2 = Duck fx vst as Alias (routed to track 03)
Track / instrument 3 = vsti with pad or similar And the Duck fx vst on the Mixer
Duck fx has a setting to change input sc - trigger from audio to midi (this too MIDI)