If Plasma Desktop is used with Wayland, using Chrome PWA (web apps) icon's are not properly shown in the task manager.
PWAs would show up as additional windows under Chrome main entry in the Task Manager.
A solution is to enable the Chrome flag, Preferred Ozone Platform and set it to Auto or Wayland.
This will make Chrome run using Wayland completely, instead of relying on XWayland, which introduces bugs like these.
Type in browser address bar in Chrome:
chrome://flags/#ozone-platform-hint
On NixOS, system wide Wayland support of Electron and Chromium apps can be enabled by setting the environment var