A DragHandler in an Item which opens a popup enables Flickable to steal mouse events from a Slider in said popup

import QtQuick
import QtQuick.Controls
import QtQuick.Layouts
import QtQuick.Shapes

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    TableView {
        anchors.fill: parent
        model: 5
        delegate: ColumnLayout {
            Label {
                text: "ABC"
                font.pixelSize: 224
            }

            Slider {
                from: 1
                to: 10
                stepSize: 1
                snapMode: Slider.SnapAlways
                value: 5
            }

            Rectangle {
                x: 0
                y: 0
                width: 200
                height: 100
                color: "red"

                Rectangle {
                    x: 100
                    width: 100
                    height: 100
                    color: "green"

                    Repeater {
                        model: 3

                        delegate: Shape {
                            required property var index

                            y: index * 50

                            containsMode: Shape.FillContains

                            ShapePath {
                                startX: 0; startY: 0
                                PathLine { x: 50; y: 0 }
                                PathLine { x: 50; y: 50 }
                                PathLine { x: 0; y: 50 }
                                PathLine { x: 0; y: 0 }
                                fillColor: "blue"
                            }

                            DragHandler {
                                target: null
                                onActiveChanged:  {

                                }
                            }

                            TapHandler {
                                onLongPressed: {
                                    var pt = mapToItem(Overlay.overlay, point.position)
                                    popup.x = pt.x
                                    popup.y = pt.y
                                    popup.open()
                                }
                            }

                            Popup {
                                id: popup

                                ButtonGroup {
                                    id: btnGroup
                                }

                                parent: Overlay.overlay

                                ColumnLayout {

                                    Button {
                                        ButtonGroup.group: btnGroup
                                        text: "Whatever"
                                        checkable: true
                                        checked: true
                                    }

                                    Slider {
                                        from: 1
                                        to: 10
                                        stepSize: 1
                                        snapMode: Slider.SnapAlways
                                        value: 5
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
        ScrollBar.horizontal: ScrollBar {}
        ScrollBar.vertical: ScrollBar {}
    }

}