[2020] Crashing upon saving new empire.

arogueplanet said: [08:38:09][virtualfilesystem_physfs.cpp:1182]: Could not open file: user_empire_designs.txt, error: permission denied

Fairly clearly something is preventing the game from writing this file out. What antivirus app do you use?

Add stellaris.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.

You may need to add steam.exe and C:/users//AppData/Local/Programs/Paradox Interactive/launcher-v2.2020.14/paradox launcher.exe to that list.