Support for this work from Benoit:

All these pre-saved messages should be community-configurable. I think that communities will ask for it; not now as most experienced users don't use their phone to edit. But when they will discover these messages posted on talk pages, they will want to review them
Community configuration should be available so that messages will be personalized. As a volunteer, knowing that a feature like this exists, I will immediately ask to add encouragement messages to the saved messages.
Also, making messages configurable solves the problem of scaling: communities can translate the contents provided locally.

The system could resemble Growth team's Community Configuration.

Why couldn’t it be Community Configuration?

If I understand correctly:

While sync (translations) can speed up getting the messages translated, they greatly restrict how much they can be customized – but these messages should be customized to precisely represent the rules and customs of the local wiki, so syncing is actually a bad thing.

Unfortunately community configuration isn't able to integrate with the app at this moment. We are working with the Growth team so that we (and other patrolling tools) can consume changes made via Community Configuration. However, they haven't gotten around to it and the apps team doesn't control the Growth team roadmap. So the planned solution is an intermediary step until the Growth team can provide an extension or API that allows us to leverage community config. We plan to continue to advocate for use of community config @Tacsipacsi .

To be clear there will also be access to community templates. Pre-canned warning Messages are available to everyone but it was more so created for medium-small language communities that do not already have templates. Each patroller can also add and store common warning messages they use locally on the device.