Extend head and tail and fade 1 frame...

Here's another variant, which allows you to have the script automatically select the scene (between 2 markers) and do the rest for you.

sf.ui.proTools.appActivateMainWindow();

function selectBetweenMarkers() {

    var markerBtnFrame = sf.ui.proTools.mainWindow.getFirstWithTitle('Add Marker/Memory Location').frame;
    var timelineFocusBtnFrame = sf.ui.proTools.mainWindow.timelineFocusButton.frame;

    var markerAreaWidth = timelineFocusBtnFrame.x - (markerBtnFrame.x + markerBtnFrame.w);
    var markerAreaHeight = markerBtnFrame.h;
    var markerAreaMidPoint = { x: Math.floor(markerBtnFrame.x + markerBtnFrame.w + markerAreaWidth / 2), y: Math.floor(markerBtnFrame.y + markerBtnFrame.h / 2) };

    var selTrackNames = sf.ui.proTools.selectedTrackNames;

    sf.keyboard.press({ keys: 'left' });

    sf.mouse.click({
        position: markerAreaMidPoint,
        isCommand: true,
    });

    sf.keyboard.press({ keys: 'l, shift+quote' });

    sf.ui.proTools.trackSelectByName({ deselectOthers: true, names: selTrackNames });
}

function ensureGridIsOneFrame() {
    /*var gridValueFieldValue = sf.ui.proTools.mainWindow.gridNudgeCluster.gridControls.textFields.getByTitle('Grid Value').value;
    if (gridValueFieldValue.invalidate().value !== '00:00:00:01.00') {
        sf.ui.proTools.gridSet({ gridValueName: '00:00:00:01.00' });
    }*/
}

function extendSelectionByTwoFramesOnEitherSide() {
    ensureGridIsOneFrame();
    sf.keyboard.press({ keys: 'alt+shift+numpad minus, alt+shift+numpad minus, cmd+shift+numpad plus, cmd+shift+numpad plus' });
}

function trim() {
    sf.ui.proTools.getMenuItem('Edit', 'Trim Clip', 'To Selection').elementClick();
}

function createFade(presetNum) {
    sf.ui.proTools.getMenuItem('Edit', 'Fades', 'Create...').elementClick();

    var win = sf.ui.proTools.windows.whoseTitle.is('Batch Fades').first.elementWaitFor({ timeout: 500 }, 'Could not find Batch Fades window').element;
    win.buttons.whoseTitle.is('Fade Preset Toggle').allItems[presetNum - 1].elementClick({}, 'Could not click preset button');
    win.buttons.getByTitle('OK').elementClick();
}

/*function showOutputWin() {
    sf.ui.proTools.selectedTrack.trackOutputToggleShow();
}*/

function goToOutputWindow() {

    //sf.ui.proTools.appActivateMainWindow();

    function openTrackOutputWindowAndCenterMouse() {
        var mainTrackOutWin = sf.ui.proTools.mainTrackOutputWindow;

        //Først: optimistic...
        if (mainTrackOutWin.exists) {
            var f = mainTrackOutWin.frame;
            if (f) {
                sf.mouse.setPosition({
                    position: {
                        x: f.x + f.w / 2,
                        y: f.y + f.h / 2,
                    }
                });
            }
        }

        var doToggle = false;
        if (mainTrackOutWin.invalidate().exists) {
            var trackName = mainTrackOutWin.buttons.whoseTitle.startsWith('Track selector').first.value.value;
            doToggle = (trackName !== sf.ui.proTools.selectedTrackNames[0]);
        } else doToggle = true;

        if (doToggle)
            sf.ui.proTools.selectedTrack.outputWindowButton.elementClick();

        mainTrackOutWin.invalidate().elementRaise();

        var f = mainTrackOutWin.frame;
        sf.mouse.setPosition({
            position: {
                x: f.x + f.w / 2,
                y: f.y + f.h / 2,
            }
        });

    }

    function ensureInputOpen() {
        var t = sf.ui.proTools.selectedTrack;
        if (t.insertSelectorButtons[0].value.value !== 'open') {
            t.trackInsertToggleShow({ insertNumber: 1 });
        }
    }

    openTrackOutputWindowAndCenterMouse();
    ensureInputOpen();
}

selectBetweenMarkers();
extendSelectionByTwoFramesOnEitherSide();
trim();
createFade(3);
//goToOutputWindow();