Add to a 7-Zip archive: How to exclude certain file types/extensions?

Only possible solution is to use the command-line version (it doesn't work in the GUI [Add to Archive] dialog):

7z.exe a Archive.7z C:\Folder\* -r -x!*.avi -x!*.flac

The "Parameters" input box in the GUI can only be used for compression parameters and cannot be used with standard command line parameters.