Is it possible to create an action to trigger a function whenever the user is composing an email?
I am hoping to add an extra button to the UI for composing emails which will insert some text into the email based on the subject and recipients of the email. Looking through the gmail addon docs I can't seem to find a way to do this.
Would this be something better suited as an actual chrome extension instead?
In short : No
For now , you can not add buttons or any other controls inside the Gmail UI. The add on does not do that. And moreover addons cannot listen into GmailUI except for triggering themselves. Thus we cannot know if the user had started typing into the compose window. It is better to create chrome extensions instead, for these kind of tasks.
Note: Gmail addons are at a nascent state. Probably, we might receive these event handlers at a later stage.