Each cel can contain some user data associated (if you want to associate data to a frame, you could create a invisible layer called “data” and then on each cel of that layer associate the user data).
Steps:
- Right-click a cel and select properties (or Frame > Cel Properties menu, or just double-click a cel)
- Click the “user data” icon in the Cel Properties dialog
- Write down what data you want to see associated to that cel:
Then the user data (text) can be accessed through the scripting API (Layer.data, Cel.data) or when exporting the sprite sheet in the JSON metadata (using -data and -list-layers).