I recommend turning graphics down to Very Low before trying this. My computer struggled with this process because it is not a super fast computer, so it may not work for you depending on your computer's stats.
First, load up the game and do Multiplayer and Create. Copy the code. Cntl + Escape to go back to windows.
Close Larian browser. Reopen it by going to your physical file location: Steamapps, Common, Baldur's Gate 3, Launcher, etc. Start a new game using the newly opened Launcher so you have multiple instances of the game open. Go to Multiplayer and Direct Connect. Paste code.
Do this for all 4 character slots until you have 4 instances of the game open and they are all connected to the same session. Have the session host Launch the game. Create characters, etc. for all 4 instances. DO NOT CLOSE any of the instances until after all four are loaded up to the beginning of the prologue where you've just escaped the nautiloid and only AFTER the host saves the game. Then close out the other instances.
This is supposed to work. I haven't ever gotten it to because my game crashes before getting to character creation.
