From the top of my head these are the OBD11 mods i did when i had my A6 C8:
* Enabling rear DRLs (Scandinavian type)
* Audio chirping when locking/unlocking car
* Enabling handbrake automatically once putting the car into 'P'
* Enabling Wireless Apple Carplay
* Remembering last 'lane assist' setting
There's loads of others available but the above i found most useful/cool
Also if not already enabled, I highly recommend getting the Traffic Sign Recognition feature enabled, this could potentially save you getting points on your licence (or worse!) as the car will display the speed limit in dashboard based on posted speed limits. This feature can't be enabled in OBD11/VCDS (well not easily at least), buying a dongle like this is the only option realistically
Coding interface for activating camera-based traffic sign recognition for Audi A4 8W, A5 F5, Q5 FY, Q7 4M, A6 4A, A7 4K, e-tron, VW Touareg CR
www.kufatec.com
But check with Kufatec first, by sending your car's VIN in case you need to return the dongle for a refund. Don't make the same mistake I did lol
Good luck!