The Breeze icon theme has an icon for the desktop, but there is no icon for a panel. This might be useful in many circumstances, but a particular area where it is acutely required is the kwin windowrules kcm. It allows the user to match various window types, and these are illustrated with icons. It currently uses list-remove(-symbolic) for this, but as the icon was changed from a minus sign (vaguely panel-looking) to a red X recently, it's now a very bad fit. desktop-symbolic would do a decent job of illustrating panels visually, but is semantically a bad fit, and the icon is already used as 'desktop' is also one of the window classes that can be matched, just like panel.
I made this 24px icon idea for the panel. Attached.
Created attachment 173102 [details] panelicon
And a variant with the plus sign emblem in the corner would be nice too. We could use that on the Edit Mode toolbar.
True, we can make that easily. Another one for removing as well?
So far I don't think we need an icon for removing a panel. We currently use the generic red trashcan icon for that which works fine since the context is obvious.