Use Case: 
Is it possible to do a mail merge of addresses for printing envelopes?

Yes it is possible. You still to create a Google Doc or Word or PDF with the proper size for an envelope. And then you can print each document on the envelope in printer. You would need to test this to make sure it all works and let support know if you have any issues or insights that they should be aware of.

To do mass printing we recommend saving Google Docs in a Google Folder and sync with desktop using Google Drive sync app and “select all” and print. Or select all in Google Drive and export all to a Zip then open on computer and “print all.”