Serrated edges, especially those on multitools like this @leathermantools Wave, rarely get sharpened.
Fortunately, DMT's Diafold Serrated Knife Sharpeners let you do just that.
Their tapered shape lets them sit in the valley of different-sized serrations. The Leatherman Wave has both large and small serrations. Find a diameter of the Diafold that fits the serration best.
Next, match the angle of the bevel. You can color the bevel in with a marker and see where the Diafold removes the marker or you can examine the scratch pattern left by the abrasive.
To stay within the serration you might have to make quite small back-and-forth movements. Try adding a little rotation to get a little extra abrasive action.
Once you've sharpened all the serrations, feel for a burr on the other side. If you've raised a burr along all the serrations then you can use any flat stone (I'm using a double-sided Diafold) to remove the burr.
It took me some back and forth, sharpening each side repeatedly to fully remove the burr, but it was such a short edge that it didn't take long.
And that's it, sharpening serrated edges is surprisingly quick and easy, especially when you've got the right tools for the job.