See the mockup below.
The task manager could use the current folder icon for Dolphin's windows (instead of grouping them in icon only file manager) to improve usability.

Pros:

• you can switch between Dolphin's windows with a single click
• a better summary in the task manager about what is running

Cons:

• if you use icon only task manager and you have 2 or more Dolphin windows with standard folder icon running, you have to look at tooltips to recognize windows without opening them (still better than the current grouping solution in my opinion)