userscripts – Automatically add a new sender address (subaddress) to GMail?

I use subaddressing constantly in my GMail account, creating a new address several times per day. However, the user experience when doing this leaves a lot to desire:

  1. Either I have to manually create a new address which is a slow and cumbersome multistep process (rather than just editing the sender field) using the web ui or
  2. use Thunderbird where I can edit the from-field but then I can’t use the GMail SMTP-server┬╣ = problems with SPF, DKIM etc.

Are there better solutions?

I imagine a solution where you execute some kind of script (bookmarklet perhaps?) that alllows you to enter the desired from-address and the script then performs all the steps required to create a new address automatically, opens a new message with the specified from-address and, after the message is sent, removes the address it just created.

┬╣ If I use the GMail SMTP-server, the from-address is reverted to the default address.