Changing Initiative in campaign theatre

[Shadowfoot]

I've had trouble adjusting characters positions during combat. What is the best way to do the following:

• Add a new character (PC or NPC) who wasn't off camera. This can be necessary due to characters actions attracting enemies from an adjacent room during combat.
• Move a character's position after they are knocked out (PF2)
• Have a character delay then act. I've seen the character's position reinstated at the point they were initially rather than the character they acted after.
• Adjust a character's position due to incorrectly recording it. (My players prefer to physically roll the dice and I sometimes put the wrong value when adjusting the value.)