I have been enjoying my 2014 Es350 for 10 years now and love it. Recently, there is a rattle in the dash driver side. I can't seem to find it. Any ideas what this could be?

 

Very hard to say anything.
Open the phone’s camera and make a video by moving the phone all over the dash, then watch the video and listen to the rattle, check the position of the phone when the rattle is the loudest.

 

Thanks to Google Gemini, it pointed me to the culprit. It was the steering wheel column damper. It even gave me the part number needed. Since the damper is used in many Lexus and Toyota vehicles, I called both my local Lexus dealer and Toyota dealer for pricing. Lexus quoted me $19 while Toyota quoted me $7. Picked up the part and found several videos on YouTube with detailed instructions. Is an ugly job but pretty straightforward. To be honest, the hardest part was taking off the A/C foot vent. Here are some photos.