how can you modify clips (for example lengthen or shorten - drag clip edges - or edit individual clips in other ways) when there are envelopes (say, volume) in place?
 
PS: I did post this as a supplementary Q in another thread, but that thread was marked as answered so I thought I'd better start a specific thread.

I might be missing the point here, but use the copy / cut / paste options.
the "Special" menus have extra features for automation.
other then that, use the track filter select clips and drag the ends of the clips.

Yeah, sorry but I think maybe you are haha! (or it's me not understanding your reply)
 
As I wrote when you grab the edge of a clip it turns blue and you can drag to lengthen or shorten it. Seems it cannot be done if there is an envelope.
Does the track filter select let you then access clips on a track if there is an envelope?

I think its not as much the point as it is the simplicity of the answer.
clips are not locked once automation is done. you just need to change the filter to clips again.
 
did you try to change the track filter to clips yet ?
you can do anything you normally can with a clip after automation is done.
just switch back to clips and its like any ordinary clip.
you can drag do what ever.
 
you might want to try opening an automation lane vs doing automation right on the track.
this free's up your track clips to still edit freely while still being able to automate it in realtime. 
 
 
I used to do all my automation right on the clips (probably like you do).
but once sonar came out with the automation lanes, it blew up my whole way of working, it literally opened up a whole new door.
 
as seen here in this video
https://www.youtube.com/watch?v=Mn5XmLRARQ8
 
and this one here
https://www.youtube.com/watch?v=jfdJFl5PJ6Q

Cool, thanks I'll check that out - it does sound like the way to do it...and yep I do the automation over the top of existing clips haha!!

WoW!! - thanks for that...that makes it way WAY easier to get things done...and it's been there since X2!!!