SUMMARY Even thought the breeze window decoration adapts to the colour of the chosen theme, the titlebar icons (minimize, maximize, close) are always the same. This doesn't look nice with many "client side decoration" apps (usually all the gnome apps). Gtk headerbar has as feature to take these icons from the current icon theme, if they are not specified in the gtk theme (see for example adwaita and plata themes with different icon themes). SUGGESTION Add an option under "Configure Breeze" to switch between breeze titlebar icons and system's selected icon theme's icons. SOFTWARE/OS VERSIONS all plasma versions since I remember (using Fedora, Kubuntu and kde neon unstable)
Seems reasonable.