I don’t know where on the list editable templates are - or if it’s even on the list - but I’ve been thinking that it could help testing. When a building gets stuck incomplete, it would be awesome to be able to shift some things around and try to identify consistent placement / proximity issues; I’ve also seen multiple adjacent rooms cause some strange edge cases it would be cool to be able to adjust or recreate on the fly.
Full disclosure: well of course I also want to be able to play with editable templates ;).
Probably isn’t a feature you’re going to see any time soon. This would be more likely to happen closer to release and only once they’ve got the new builder working 100% to their satisfaction first. We can’t even edit builds that are in progress or modify buildings after they’ve been built, so I think these would be more likely to come first and would be quite a difficult and lengthy development/bugfixing process in and of themselves.
The workaround for this at the moment would be to place a new instance of your template down but edit it before you hit “build”. You will be able to edit it in that way and then re-save it as a new template. You can remove the old/deprecated templates from your “\Steam\steamapps\common\Stonehearth\saved_objects\stonehearth\building_templates” folder by deleting the .json file and its accompanying .png thumbnail.
If you’re really into building templates it might be a good idea to start a fresh game in peaceful mode and use this to design and test out all your buildings, developing a suite of your own varying templates you might use in your main games if you don’t like using the premade ones the developers have provided. You can spawn in resources using the debug tools “item stamper” as well, so you won’t be effectively playing a full game just to develop your templates and test building AI. I think the debug tools are now included in the game by default but you need to enable it in your mods or options.
Hope this helps you find some workarounds until they get closer to release and start looking at “polishing” projects like this.