Feature Request: Panel Icon Customization

Hello,

I frequently use different themes in XFCE, and I often encounter situations where the default panel icons do not match the desired style of my setup. For instance, the "Show Desktop" icon often stands out and doesn't fit with the rest of the theme, and the same issue can occur with other icons as well.

It would be incredibly useful to have an option in the panel settings to individually customize each panel icon, similar to how it is possible with launchers. This would allow users to replace specific icons with custom ones that better fit their overall theme, providing more flexibility and coherence in the desktop appearance.

Thank you for considering this request!