There are great tools out there already to generate shapes in the automation editor like automasher ( https://www.renoise.com/tools/automasher ) & automatron ( https://www.renoise.com/tools/automatron ), if only these tools would also let you output to the envelope device in the instrument editor.
I know you can generate shapes from above said tools, copy & paste from the automation editor into an envelope device (and/or lfo external editor), but the shapes wont automatically scale into a set envelope device length.
I think the envelope device is one of the most powerful modulation options we have, but has much more potential that could be more easily tapped into through tools. For Renoise 2.8 there is a tool where you can have envelopes generated for the envelope device in the pitch tab from the instrument editor based on the note events in the pattern editor ( New Tool (2.8): Notes to Envelop ), unfortunately 4teys hack for 3.1 is lost with the forum migration.
Afta’s Reseq ( New Tool (2.8): ReSeq ) would be the ultimate envelope pitch controller,…
…but that one also stopped working after Renoise 2.8 
May the script gods please fix above issues or create a tool for ultimate envelope device mangling.
Cheers.