At any rate, outside of Distort FX the main way to curve text in OpenToonz would be to use the Plastic Tool.
- Draw a simple rectangle and use that to create a Plastic mesh.
- Then add some text to another level and make sure it fill fit inside the shape of that rectangle
- Build the Plastic Skeleton so that it has enough nodes to be able to distort the shape without awkward breaks etc.
- Parent the Text Level to the Mesh level (and disconnect the Rectangle level... you don't need that any more)
- Animate the Plastic Skeleton to bend the text.
Render and adjust to taste.
Serve with dessert.