I’m using Plasma 6.1.4 on cachyOS, and I am having trouble re-arranging my taskmanager icons. I can switch positions for some of them, but not all of them. For example in this screenshot I can sometimes switch the places of the rightmost two options by clicking and dragging, but I cannot move Konsole. Sort is set to manual, settings are default.
If the icons have been pinned to the Task Manager widget (via right-click in the application menu) then they can be moved around on the Task Manager widget. If you drag to the panel, you may actually create separate launcher widgets depending on where you have dragged them. These are not part of the Task Manager widget at all. As widgets, you need to use the Edit Mode/Show Panel Configuration to move these.
This post and short crude video sort of demonstrate this a little, with the task manager widget sliding out of the way when dragging a menu item to the panel, to the left of it.
A quick way to tell is to right-click on each icon and see if you have the option to pin /unpin.
A bit more from a post I made here
Thank you for the fast reply, I get how it works now and have fixed my setup.