Task Manager widgets currently offer a number of sorting options, among them "Do not sort" and "Manually". This is nonsensical as these mean the same thing to most people, but don't do the same thing: one lets you manually drag them, another locks them in place but doesn't let you choose the arrangement at all.

I would recommend removing the "Do not sort" mode and replacing it with a feature to lock the icons' current positions — which appears to be what people are using "Do not sort" for, even though it doesn't 100% work for this purpose since the icons can still be moved if the underlying model changes.