Afaik there is not the same option. You could use your own keyboard shortcuts. The option to send the prewritten messages only appears with an incoming call to reply fast to the caller.
[You could create a template message using Shortcuts then add a voice trigger. That would be actionable from the Watch. The limitation would be that it would basically be a non-interactive message for each trigger, e.g., telling your SO that you are on the way, but you couldn’t then use the same trigger to send a message to your boss or a friend instead.
You can build customisation with Shortcuts, but interactions only work on the iPhone / iPad.]
Sorry - misread your original message. You are on the iPhone
Try building it in shortcuts, I have one that works out how long it would take to get home then sends that info to my wife.
Another thought - have a shortcut that loads the message into your clipboard then just paste that into the message field. It depends what aspect of the process you are trying to automate.
If you have a number of set messages that you send on a regular basis you could probably have one shortcut that you run from the widget screen or home screen. When you press the run the shortcut it could give you a menu asking which message you want to send and then either load a new message with it loaded in and you add the recipient or potentially you could set the shortcut to have the recipient pre loaded if its the same person each time or even have the shortcut ask who you want to send it to.
I have a couple of shortcuts that incorporate messages, one asks whether my wife is at home or work and then works out how long it will take to get there, convert that travel time to what time i will get there, send a message to her saying i will be there at this time and then loads up the directions in Apple Maps for me. Another one is much simpler for when i drop my daughter at my mums before work, simply sends a message to my mum telling her i'm just leaving my house and then she knows when to be at the front door for a quick handover of my daughter on the way to work!!
In addition to Shortcuts, you can use the Notes app.
Select the message, tap the Share Sheet, then either Messages or Mail.
With templates in Notes, believe you can extract the text from the note via Shortcuts and then pass to the email or Messages methods to send. So, options there.
You used to be able to define custom substitutions IIRC? Like, type ‘omy’ And it converts to ‘on my way’. That conversion actually happened whilst I was typing this post, and I had to change it back manually...
You used to be able to define custom substitutions IIRC? Like, type ‘omy’ And it converts to ‘on my way’. That conversion actually happened whilst I was typing this post, and I had to change it back manually...