It is obvious and unavoidable that there must be **a change**.

The biggest problem with the proposal is there are **two** changes, not only the addition of a new button `1` but also a new action area different from the already established `1` and `2`

[![new action area][1]][1]

> What are effective ways to introduce this change without disrupting users' workflow?

Do not add more changes than those that are necessarily necessary

Personally

1. I would keep **a single action area** with the simple addition of the new function button
2. Color code keeping the same scheme for better identification of the new component

[![three buttons][2]][2]

[1]: https://i.sstatic.net/8WkLzTKZ.png
[2]: https://i.sstatic.net/nSW3ceVP.png