For Unity take a look at Ink, Yarn, and Node Canvas's Dialogue Trees. Currently using the latter for a large project and it's worked out. Ink has a high learnin

For Unity take a look at Ink, Yarn, and Node Canvas's Dialogue Trees. Currently using the latter for a large project and it's worked out. Ink has a high learning curve. Yarn and Ink will both require a fair amount of glue to connect to Unity -- Ink moreso. You might also check out Unity's Timeline functionality for scripted sequences.