I've tried the ways in official documentation told me. I have tried to delete all the automation nodes or lanes, it seems to work at the moment. But every time when I open those lanes again, those nodes and envelopes appear again! I even can't reset all automations and return their values to "new project default". Automation nodes seem like can never be deleted and forever exist.
 
So how can I permanently delete them?

right-click on the envelope line and select "Delete Envelope"

I've tried and it doesn't work, the deleted envelope appears again and still controlling my instrument synth.

Opening the automation lanes on a track without any automation lanes defined with create a volume envelope by default. It will have two nodes, one at the beginning of the track and one at the "end" of the track. Other than that, delete has always worked for me to remove an existing envelope (including a freshly created volume envelope).

I've followed your instructions and deleted all envelopes and never open them again. But when I tried to control the volume inside the interface of my VST instrument plugin and play it, it automatically controls my volume fader again back to the deleted node value.


So how can I make sure all the automations are deleted and control nothing?

There is more going on than automation in the instrument track. I rarely adjust the volume in a plug-in. It might have something to do with the plug-in itself or another setting like "Zero Controllers When Playback Stops"  or the plug-in might be picking up controller data echoed from another track.

How about in kontakt, trilian, omnisphere realguitar and toontrack superior drummer?

OK, as a test, I create a new project with Superior Drummer in an instrument track (the only one of the plug-ins mentioned).

• Set the volume in the mixer in the SD UI and nothing changes the value.
• Reset the volume in the SD UI
• Add a volume envelope and add some nodes
• Test the track, the volume follows the envelope
• Delete the envelope, reset the track volume because the envelope could have adjusted the volume on playback and deleting the envelope does not alter the current volume fader setting.
• Adjust the SD UI mixer volume
• Project now follows the SD UI mixer volume setting

It should be the same in any project but as mentioned above review the preference and input settings.

so how can I reset the track volume?

I use the volume fader on the track