Photoshop is terrible. I think we are on the same page with that! 😃 Unfortunately it's widely used and has scripting support. It's not that we don't want to support other apps, it's just not always possible. SAI doesn't appear to allow writing scripts/plugins.
The same is true for other apps, like Clip Studio Paint. We use that and would love to support it, but they don't have scripts/plugins and they aren't interesting in putting in Spine support themselves.
Affinity Designer also doesn't scripts/plugins, but they are awesome and added Spine support themselves. Unfortunately it's not as powerful as the Photoshop script. We talked with them about improving their support, but it's a lot more complex than the basics they did and they understandably don't want their time sucked away fixing bugs in their implementation. They didn't actually say no, but they haven't done it yet either. Anyway, Affinity Designer could be a somewhat less powerful option. If they had full support like the Photoshop script, we would happily push everyone to use Affinity Designer.
Another option is to use Photoshop CS2. Adobe made that free a while ago, or something like that, and it is very easy to find the official, unprotected software, no crack needed. It's super old and crappy, but it can run the PhotoshopToSpine script. If you can export to PSD from SAI, you could use CS2 to process the PSD into files Spine can consume, giving you all the PhotoshopToSpine script features.
We've discussed many times a way of supporting exports from any image editing software. Most software can export layers as PNG files and we could have Spine process [tags] in the PNG file names, but unfortunately the layer folder hierarchy is lost. That makes it a lot less useful.
