could not find the old thread, oh well, here's a new one.

???
 
(maybe it's just me, but i don't get what you are asking for ...)

I have this great flanger, for example, called Liquid, which to my deepest regret does not have an integrated mix knob. now, this would not be an issue at all, were I using a daw with a well featured mixing environment, which would naturally include a mix knob for each plugin container. Sadly I use Sonar instead.
 
It's quite depressing having to make requests for things like this. I could probably think of a lot of innovative, cool stuff if I didn't rather have to think about why or how Sonar doesn't yet have a mix knob for plugins.

If you absolutely must have mix level control, I'd add the flanger to a bus and use a send.  I get the request, but at least this would give you what you wanted now rather than later. 
 

yeah sometimes I do that, or just stick it in a MUX instance. it's slow and cumbersome though. my biggest gripe about sonar in general is how the whole thing seems based on workarounds instead of intuitive functionality. they should work on that aspect imo.

Ah, I also have MUX - very convenient to have on hand.   I don't necessarily find it slow or cumbersome, though it's not something I need to use that frequently.  If anything I use it more to chain plugins together, when needed.