Wait a minute... all Wine applications are grouped together and cannot be pinned to the taskbar.

All Wine apps being grouped together is a known bug that was fixed in a recent 5.8.x point release.

Pinning Wine apps: To pin an application, the Task Manager needs to take a look at the window and find out some way to restart the application that owns the window later. This is done by looking at window metadata and other, indirect data sources, and a very complicated procedure on X11. Wine apps are unfortunately one of the hardest types to get this right for, because their window data is really shoddy and in most cases makes it impossible to deduce a menu .desktop file name or command line from the window reliably (i.e. without hacks that break other things).

Wayland will hopefully help there - once Wine supports it - by forcing Wine to provide a proper appid for the windows ... although to be honest I am not holding out that much hope they won't screw it up.

Basically, it works fine with well-behaved apps, and we try quite hard to account for the ways in which apps often do not behave well, but Wine is unfortunately among the worst.