How can I use Gmail's canned responses on my phone? I frequently use canned responses in Gmail on my computer but it doesn't seem to be accessible on my phone. Are there any workarounds or solutions that allow me to use this feature on my phone as well?
As of July 2019, the features is not available for Gmail app but you can use it when using a browser on your phone and requesting the desktop version.

You are left with 3 possible solutions:


Create draft messages that you can then copy and paste for new messages.
Enable "Smart Reply" in the Settings of the Gmail app for the account you are using. Then hope that you will get good suggestions when replying to messages.
Use Canned Responses for GMail. It purports:


  GMail canned responses are very handy on a full featured web browser but when it comes to mobile - it's almost impossible to import your canned responses in an email message. With Canned Responses for GMail you will be able to do it in 2 taps. A swipe and a tap actually :)