I’d like the ability to import multiple images, such as frames from a video clip, that can be used as a reference. This would be similar to the current ability of displaying another project within a selected layer, but optimized for animation: mainly, importing a series of frames to be used for rotoscoping.
You can load a series of image files the following ways:
into a new project: menu File/New Project/Create from single Images
into an existing project: menu File/Animation/Append single Images…
You can simple use them in a lower layer (or even a top level one with low transparency) or attach it to another project with the display other project technique.