I\’ve tried to extend the base a few times, but it seems that only connectors snap in place of other connectors. If I try to build a storage, I can\’t merge it with the base. The only way was to build an airlock facing the entry of the storage, creating a sort of V shape, where the airlock stairs overlap each other, but that\’s also a texture bug.

Development Comment:
Thank you for the report, we tried to reproduce this problem but we are unable to.
If you could provide a bit more information about this problem, is this in Midway Branch or the Main branch? Did this happen with all the buildings or just the Storage building?
Bug seems to be already fixed in the Midway branch, just in case I’m providing link to the short guide on how to access it Steam Community :: Guide :: How to access Midway Branch of Penkura . The entire Midway branch will soon merge with the Main branch, your save files should without any problem recompile to the Midway branch, and when moving from Midway Branch recompile back to Main Branch after the merge (no need to start from the beginning).