Okay, I have tested it and can show You what to do. To get the rounded Corners, You type in the Terminal:
sudo nano /usr/share/gnome-shell/extensions/zorin-taskbar@zorinos.com/stylesheet.css
I created the #panel Value here:
So, I typed in the whole Block:
#panel {
border-radius: 5px;
}
and it worked like You can see here:
And it works over the whole Length:
