Working on the post. Just need to clarify one last thing: since they're up 10 feet above the ground, trying to jump down would cause them to take fall damage, right? If so, can Flicker jump down and attack (using Produce Flame) even if they take damage? (Sorry, still newish to 5e, not fully comfortable with combat rules ^^;)
If not, I'll probably just attack using Produce Flame from the window.
In my experience, depending on the DM they might have you make an acrobatics check to intentionally jump down that far. Fall damage is 1d6 for every 10 feet but, smaller, intentional jumps it depends on the DM.