goodbye to the K, hello to the Swirl

Clicking on the big "K" icon on the KDE Plasma 5 panel brings up the Application Menu -- aka, at least in the old days, as "the KMenu." That icon is shown here, at the bottom of my left-side, vertical panel:

In Debian 9 ("Stretch"), I prefer a Debian logo icon. To change it, first I right-clicked on the "K" icon and selected "Application Menu Settings...":

In the Applications Menu Settings window, I marked the box to "Use custom image":

Then, over to the right of that, I clicked on the folder icon:

In the "Choose an image" window, I navigated to the /usr/share/pixmaps directory and selected debian-logo.png:

Then, back in the "Application Menu Settings" window, I clicked the "Apply" button:

All finished: