only 2017, or did you work on this in 2016 already?

this name is too generic, it's only for copy'n'paste, right? Maybe call it CopyAndPasteTaskInfo? I'd also welcome if you could move this to a separate file, along with the create*Widget helpers

mark this as Q_DECLARE_TYPEINFO(..., Q_MOVABLE_TYPE); use QVector instead of QList below

join with next line

dito

dito

I'd welcome if you could move the ui setup stuff into a .ui file created with designer

could you move this stuff into separate helper functions? this looks like multiple steps, and readability would be improved if each step would be its own function

does this need to be sorted? if not, use QHash

again, QHash

de-inline for readability, join next line, i.e.:

const bool anyFailed = std::any_of(tasks.begin(), tasks.end(),
                                   [](){ ... };
if (anyFailed) {
    ...
}

add a TODO to create a model for the task list, and use it here instead of using QTreeWidget

also here and elsewhere: do not use foreach, use range-based for

again return a struct, instead of using out parameters

add braces

rename to mapSourceToDestination, return a struct with the mapping instead of taking two out-parameters

rename first paths argument to sourcePaths, rename destPath to destinationPath

please use an enum instead of a boolean here

rename to showWarningDialogForFailedPaste

add braces