Is it possible to add more memory to Mac mini M2?

No.

If you are having issues with the M2 Mac mini.

Download and run the free version of EtreCheckPro, from > https://etrecheck.com/en/index.html

Then post your Report, as per > How to use the Add Text Feature When Post… - Apple Community

Do you need more? Have you got a problem caused by lack of memory?

FWIW I have never had more than 8GB RAM and it has not caused any problems editing 1080p and 4K videos in Final Cut Pro and DaVinci Resolve.

No. Expanding RAM is not possible on any device with Apple Silicon.

Regards.