Quote email from lead

I found the below on another part of the forum but unanswered i too have this issue any help apprecitated

We regularly send quotes by email (with attached PDF). We don’t use Contact/Accounts modules, instead we link Quote to Leads. Here’s our workflow:

  1. open quote record
  2. choose “Email PDF”
  3. select PDF-template
  4. Select Email recipient (which is a Lead already linked to Quotes record)
  5. select Email template
  6. Send email

How could we automate step 4? i.e. prepopulate Email recipient based on Lead record that’s related to Quote record?