Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding Troubleshooting Make a NPC sit

For everyone still wondering:
1. Make sure the chair you want to use has a name that starts with "S_". This is used by scripts to filter items that are supposed to be assigned in script parameters.
2. Select your character and in the Sidebar property "Scripts" add the "Sit" script
3. Select the assigned "Sit" script and in the "Seat" parameter, select the chair you just name S_MyAwesomeCharName

And presto, once you go into game mode, the character will casually walk over and sit on it.

PS: The Sandbox has a couple of sitting people. It was filled with a bit of everything, so browsing through that level often helps in finding how something simple is set up.