I’ve tried to work around this by taking the the kick and bass into a send channel and using the gate. Its doesn’t fully do the trick because its still a blend of both track. this is something I’ve been waning for years.
Please give renoise a side chaining ability.
It’s called creative use of the Signal Follower!
Or rather the not-so-creative use of it 
That make a hole new world for me! thanks! 
Look into a plugin called SideKick by Twisted Lemon. It will do proper sidechaining in renoise.
Unfortunately Renoise does not yet support multiple inputs for VSTs so it’s not possible. For now use SideKick and keep your fingers crossed.