[game version 1.1.2 stable steam] Hi, when the planet reaches the maximum population and then you build the subsurface vault, the Planetary Engineering slider will still be locked.
Hello, well unfortunately the lock is permanent and can not be changed with a padlock icon. Check on my save, planet Terronda III (J2 sector).
Hi again To unlock, click where I have circled in red, I know it's kind of tricky but until you enable habitat control, the padlock remains inoperative