How to evoke Preview's title bar saving dialogue by shortcut?
You can use Automator/Apple Script for this with Mouse Tools command line app.
You can get Mouse Tools from here. It's a small tool to move mouse pointer and perform clicks.
[-h] return this help text
[-b] coordinates are measured from bottom-left corner of the screen
[-location] return the current mouse location
[-x &quot;xValue&quot; -y &quot;yValue&quot;] move the mouse to the {xValue, yValue} location
[-mouseSteps numSteps] move mouse in number-of-steps to the location
[-leftClick] perform a mouse left-click at the current mouse location
[-doubleLeftClick] perform a mouse double-click with the left mouse button
[-rightClick] perform a mouse right-click at the current mouse location
[-shiftKey] shift key down, useful when performing a left-click event
[-commandKey] command key down, useful when performing a left-click event
[-optionKey] option key down, useful when performing a left-click event
[-controlKey] control key down, useful when performing a left-click event
[-leftClickNoRelease] perform a mouse click and do not release the mouse click
[-releaseMouse] release the mouse after using -leftClickNoRelease

Then create an Automator workflow as a Service. Set &quot;No input&quot; as an input and &quot;Preview&quot; as an application. Add this Apple Script there:
on run {input, parameters}
    tell application &quot;Preview&quot; to activate
    delay 1
    set mouseToolsPath to (path to home folder as text) &amp; &quot;Downloads:MouseTools&quot;
    tell application &quot;Preview&quot;
        set _b to bounds of the front window
        set _x to item 1 of _b
        set _y to item 2 of _b
        set _width to item 3 of _b
    end tell
    set xpos to _x + (_width / 2)
    set ypos to _y + 10
    do shell script quoted form of POSIX path of mouseToolsPath &amp; &quot; -x &quot; &amp; (xpos as text) &amp; &quot; -y &quot; &amp; (ypos as text)
    do shell script quoted form of POSIX path of mouseToolsPath &amp; &quot; -leftClick&quot;
    return input
end run

In this case, my MouseTools binary is in Downloads directory.
Save it and give it a name You'll remember. Assign keyboard shortcut to this Serivce in Preferences.app under Keyboard -&gt; Shortcuts.
I tested this and it works for me.