Currently, when there is a duplicate task, it is grouped in the panel and identified with a symbol. This causes a series of problems, since depending on the icon of the application, the symbol can "blend" with the icon and you won’t be able to see it. As it can happen in the event that a popup appears in Firefox and you don't realize it until much later.
It also doesn't communicate adequately how many open windows you have. Returning to the example of Firefox, you can have several windows open for various reasons, and not realize that a popup has appeared because the icon remains the same, since another window is already open.
The option to change the symbol by duplicating the task icon would not be very effective either, since depending on the icon it can look blurry, and end up oversaturating the panel. An option similar to the one implemented by "Fancy Tasks" would be more appropriate, and people seem to like it quite a bit.