I use Aseprite primarily for gamedev, and I’d been looking forward to the tile editing features of 1.3. I’ve been doing my tile work in PyxelEdit and Photoshop, and Aseprite’s tilemap UX improves on a lot of the annoyances in both of those. Unfortunately, it looks like Aseprite has followed in the footsteps of Pyxel Edit when it comes to tileset management - tiles are second-class, tileset management is very basic.
For game development, it is the tileset itself which is the primary deliverable asset, the main canvas is only there for testing things out. Live tile updates are great, but are useful for only a small part of the tileset creation process. Tileset organization is very important, a well-organized tileset can save a level designer hours of time in selecting the tiles they want to place. Tilesets can also be works in progress for a long time, and it’s often beneficial to leave some space for future tiles, so that related tiles are in the same region of the tileset. On the other hand, the future tiles aren’t always known far ahead of time, so sometimes one has to move an entire region of the tileset to make room for a new group of tiles. These kinds of management tasks are technically possible in Aseprite, but they’re very annoying, as there’s no fixed width to the tileset and no way to pan around it, no way to move a bunch of tiles down without shifting other tiles around, etc.
With Aseprite and other software I’ve used, much more practical to make tileset management a separate step, done after testing the tiles - arrange them on a regular document along with other tiles. Layers can be used to group tiles for easy movement and adjustments. The downsides to this method are that there’s no way to ensure all tiles are included in the output and that every tile is only included once, arranging the tiles hours after you’ve drawn them can be difficult if you didn’t previously arrange them in the tileset in a way that makes their purpose clear, and that the testing document doesn’t benefit from this arrangement.
It’s also often helpful to use layers within tiles, while using the composite tile as a simple tile. For example, one may want to try a few styles of grass on top of a rocky sidescroller tileset. Each style of grass would be its own layer, and toggling the visibility of the layers would affect all instances of that tile currently in use. This is not possible in Aseprite, I would have to make separate tiles for all the grass and place them on separate tilemap layers, and toggle those, and then copy+paste the final grass onto the rocks base layer (can’t even Merge Down; since that’s not well-defined for Tilemaps where different tiles can be stacked together).
As you can see from these workflow descriptions, for a powerful tileset editor, the tileset itself needs to have some of the same features as the main document. Layers (internal to the tileset, with only the composite results being used in documents using that tileset), a definable size or at least some way to assign each tile an x,y position on the tileset without necessarily shifting over a bunch of other tiles, creating/leaving empty tiles as needed, some way to define groups of tiles so that they can be selected quickly to be moved (layers are only a stopgap measure for this, as moving the pixel data doesn’t update the tile indices, whereas proper tile arranging should).
An alternative to making tilesets a nearly full-fledged document and adding all of these features would be some tools to automate the management of tiles in a separate document. This would require documents to be able to share tilesets, so that changes propagate. It would also require some way to limit each non-empty tile to being used only once in the document. In such a limited document, Merge Down should become available since it would no longer be ambiguous. Unused tiles in the tileset should be highlighted, to help make sure every tile is included in the document. While this wouldn’t help with making convenient tilesets to use within Aseprite, it would make the exports much easier to arrange and maintain.
I don’t expect Aseprite to get any of these features, but I can dream :] I don’t think I’ve seen any editor that gave tileset management the attention it deserves, tileset creators have been arranging their tilesets manually for decades, wasting the time they could spend on adding more tiles.