I have a few extra lives and I hit a difficult battle where I used 2 of them automatically. I didn’t want to use them, I could have died and tried again and saved those extra lives for a boss fight or something. I checked the settings and don’t see a way to change but I’m wondering if there is something I’m not seeing? Is there a way to change it so that the extra lives are used only when you want or even let you see a prompt to decide when you want to use them?
It’s not possible to save them up. I guess it would make the game too easy on the harder difficulties. You could save them all up and get through the hardest parts with no difficulty since you are essentially invincible. You will have to reload a game save or something if you want a second chance at an area but want to save the extra life.