You can extend the envelope’s overall time , by just clicking or draggin.
The speed of the shortest envelope section is dependent on the underlying tpl engine
I have asked this before ( 2 years ago -) , nothing since .
Lot’s of things can be improved in the instrument section , also the drive is always post envelope ( it affects the envelopes shape )
And yes ,the envelopes aretoo slow ,
https://forum.renoise.com/t/the-envelope-and-its-quirks/45178
And let’s bump my old thread 