Sorry for just writing a random message but wouldn't it be possible to make an 8k map by making the height map res 8192 px? I made some testing and didn't run into any problems. maybe you could add a 8k version of your template map.
The assets in the asset browser? Did it just stop loading suddenly? Could you send screenshots of the console? Might be something useful there --- Post updated --- I don't know, I guess you could try that. Another way would be to use a 4k height map and setting the meter per pixels lower so it makes an 8k terrain, but then painting will be less accurate.
