The replace function opens an additional menu depending on the item that is selected in the stage. Selecting a character and clicking replace opens the character panel. Selecting an asset and clicking replace opens the asset panel. Clicking replace without an item actively selected opens the template panel. Once a panel is open, select a new item to replace the existing item, then save to complete the process.
The replace function only works in the active scene - it does not replace assets throughout an entire video or all scenes.
1) Select a character (or any other asset, template, or item) in a scene.

2) Click Replace in the toolbar.

3) Select a new character in the panel.

4) The new character is then replaced in the scene.
