One of the most enjoyable parts of Linux is the degree of custom theming.
Some examples of my own novice making;
Azenis 2021* on XFCE 4.16 Desktop -installed on Zorin 16 Beta. This includes theming the Whiskermenu (Above on Vertical Panel) and the Zorin Lite Menu (Below on horizontal panel).
XFCE 4.16 includes CSD's, so you can see in the below screenshot, csd's are themed in, in addition to the XFWM4 window borders.
Cinnamon Desktop and Mate Desktops are also themed in, with vertical or Horizontal Panels very similar to the ones shown here.
This is not available in Gnome or Gnome shell, nor have I any intention of doing so-- However, I would hope to encourage others to enjoy customization of their own Gnome desktops, as they see fit. (The gtk portion will work in gnome3 and gnome 4.)
You need not make an entire theme of your own, but by utilizing your ~/.config/gtk-3.0/gtk.css file, you can theme in snippets at a time. FOr example if you like your system theme but wish scrollbars were wider- or had stepper buttons. Or if you want to reduce or increase the size of headerbars and so on.
Also... Willing victi... testers wanted who would be willing to test my themes to help me find bugs, missing portions, etc.
*Azenis was originally created by J.J.Ying for Microsoft Windows. This was closely followed up with Azenis2. Azenis2 was ported by EZY to KDE Desktop and later, JamesHardy88 ported it to Gnome2 gtk2. This is a gtk3 /gtk4 port for the year 2021, also celebrating 15 years of a classic Favorite. Azenis2 was the base model for this recreation.