Am I missing something or is the only way to empty the cache is to manually delete the files?

You can also set the cache-size to 0, close K-Meleon, restart it and set the values to the previous ones. But it's not comfortable. I'd like to have a button "Delete the cache", too.

I put a shortcut to my cache folder on the start menu.Just one click and there are the files to delete.

Where is "cache folder"?

Andy,

The location depends on your operating system but it will be located in your profile directory in this order:

KMeleon\Profiles\default\*.slt\Cache

Andrew

Andy,

Mine is located in c:\windows\application data

Combining the answer of Rab,followed by Andrew's,the location is correct,i.e
c:\windows\application data\kmeleleon\Profiles\whatever your profile is or default\blahblah.*.slt\cache. It is actually easy to find.