It is now possible to add Google Drive documents into a Gmail mail, after our latest {click} command update in May 
See the full snippet with notes:
{note: trim=yes}Click on the attachment button in the Gmail compose box{endnote}{click: selector=td.bzE div[command=docs]}{key: enter}
{note: trim=yes}Wait for the attachment frame to load{endnote}{wait: delay=+5s}
{note: trim=yes}Click into its search field{endnote}{click: frame=top; selector=iframe[src^="https://docs.google.com"] |> input + input; maxdelay=+10s}
{note: trim=yes}Insert the search term and hit enter to search{endnote}search term{key: enter}
{note: trim=yes}Select the first result by clicking it after it appears{endnote}{click: selector=div[id][aria-selected=false][data-target]; maxdelay=20s}{key: enter}
{note: trim=yes}Click the "Add as link" button{endnote}{click: xpath=//*[contains(text(), "Add as link")]/parent::button; maxdelay=5s}
Here is the same snippet without the notes:
{click: selector=td.bzE div[command=docs]}{key: enter}{wait: delay=+5s}{click: frame=top; selector=iframe[src^="https://docs.google.com"] |> input + input; maxdelay=+10s}search term{key: enter}{click: selector=div[id][aria-selected=false][data-target]; maxdelay=20s}{key: enter}{click: xpath=//*[contains(text(), "Add as link")]/parent::button; maxdelay=5s}
Let us know if it works for you.