It doesn't work in android app: "To add a priority while adding a task, you can type !p1, !p2 or !p3 within its name"
This was intentionally left out of the android app since using special characters can be difficult in mobile devices. As you know, you can do this already using the "edit" option. We may consider finding a faster way of setting priorities in the future.
any special characters isn't problem with using user dictionary.
So I'd like to mention about FIVE taps using "edit" option.
Just because it is more difficult to enter a particular character it would seem to be short sighted to limit functionality when it's available in a companion App. Eventually these get noticed and it is just annoying. For a user it is confusing and we have to try and remember what works with each App. Keep it simple please.
One of the strengths of Todoist is that it is cross platform. To keep customising features for a particular App seems counter intuitive to me.