Every time I try and change something on my VSTi - whether im Renoise or on the pugin itself, it defaults back to a certain setting as though those settings are locked.
I did create a pattern automation previously via the graphical envelopes, but can’t seem to delete it or amend it anywhere.
Here’s what the screens look like:
and
I’m stuck at this point and can’t find any way of getting around this - I’ve resorted to random button presses and a mouse clicking frenzy 
Is there some way I can wipe all automation for that VST and start again without having to rewrite the whole song?
Thx.
I have learnt a valuable lesson - better to use multiple instances on the same VSTi if used on different parts of a large song - espescially if it’s heavily manipulated.
Easily achieved using using the Swap facility in the edvanced editor. Another superb function in Renoise 
And to perhaps learn to walk before you run, ie: by starting off a little bit smaller when trying to learn the ins and outs of Renoise, rather than doing battle with a 20-minute epic rave mega beast like Jesus On E’s. 
Still… I really admire your determination. Be sure to let us hear what you do with your version
VSTi also usually only have a single output stream so you can’t actually play them correctly on two tracks at the same time.
Didn’t know about the Automation Deletes outlined by Bantai but you can also remove all Automation from a Track, Patter, Song etc via the Advanced Edit using the Masks. Not as useful in most cases but if you wanted to remove every piece of Automation in a Song may be the faster way to go about it.
automation is one of the few weak points left in Renoise.
maybe they’ll think about it …
I’ve found that some VSTi’s are fine when played across two tracks (I generally use Korg M1, Vanguard and Nexus.) although using automation like the Gainer will not work properly if this is done.
I’m going to use the masks in advanced edit as you suggested - this is a great way to undo everything when you’re experimenting - great advice!