As a Roblox developer, it is currently too hard to use the 9-slice editor when assets are not yet loaded.
Ever since the release of the 9-slice editor in December 2021, if a developer tries to open the 9-slice editor on an image that has not been loaded yet, the editor will throw an error as seen in the image below.
This current behavior seems incredibly silly. If Roblox Studio is able to identify that an image is not yet loaded, I would expect it to just load the image right then and there. Roblox Studio already automatically loads an image when you insert a Decal into the Workspace with an image id that has not yet been loaded, or if you display a GuiObject with an image that has not yet been loaded. And so I would expect the same behavior here.
Apparently this issue was already reported and acknowledged during the beta of the feature, but it seems it was not worthy enough until now. I understand that the lack of this feature may not be a game-breaking problem. However, to me this feature seems like incredibly low-hanging fruit that makes the overall development experience in studio a whole lot less frustrating.
Please consider revisiting this feature. 