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.
Also
7za -bt -mx9 a archive.7z d:\backups\* -x!*.7z
and
7za -bt -mx9 a archive.7z d:\backups\*.* -x!*.7z
Created different result. The one with *.* seem to work.