Which skills can be leveled outside the raid?

Yes, at least one more skill gains experience through actions in stash:

• Weapon maintenance: Experience is gained through repairing weapons

Experience is gained through actions in hideout for these skills:

• Hideout Management
• Crafting

These skills appear broken:

• Metabolism: Appears to gain experience through actions in stash, but progress is lost upon reloading profile (e.g. entering a raid)
• Intellect: Neither has effect nor gains experience outside of raid

All others skills: Only gain experience in raid (progress is saved to PMC/Scav character) or through quests that upon completion add fixed amounts of experience points or levels.