A feature to pin or bookmark specific animations for quick access hasn't been implemented yet, but it would indeed be useful when working with projects that have many animations.
Currently, there are a few ways to organize and access your animations more efficiently:
Animation Folders
You can organize animations into folders to keep them structured. To create a folder, select an animation and click New... → Folder. You can then move animations between folders by dragging them. This helps group related animations together, making them easier to find.
Animations View
The animations view provides quick access to all animations for the selected skeleton, eliminating the need to navigate through the tree to find the Animations node. You can access it from the view tabs, and it lists all animations where you can quickly click to switch between them.
While these features help with organization, I understand a pinning or favoriting system would provide even faster access to frequently used animations during development. If this is something you'd like to see added, you could submit a feature request on the Spine Editor GitHub issues page where the development team tracks feature suggestions.
