Thanks so much for playing! I'm really glad to hear you're enjoying Serenitrove. I try to fix bugs and push out updates as quickly as I can in my spare time, and a lot of the balancing improvements have come directly from community feedback. So thank you for being a part of that.
New zones will definitely be added in the future. The main reason they haven't appeared yet is because I'm still in the planning phase, thinking through what the new environments will be like, what kinds of challenges they'll introduce, and what kind of new resources will spawn there. Each new zone opens the door to adding new materials, which means designing new tools, accessories, consumables, and even revisiting the backpack system to support more than 3 consumable types (storage system?). So it's a pretty big chain of changes, and it will be rolled out as a major update when it's ready.
About the warning icon, it only appears when you don't have enough stamina to dig a particular block, but you're not completely out of stamina. For example, if you have 1 stamina left and try to dig a gem block with a hardness of 3, the icon will show up. But if you try to dig a regular sand block with 1 hardness, it won't.
As for quickly moving ores, do you mean holding down the + button on the furnace?