[NAME]  I am assuming that LCD is just cracked but still connected to Motherboard, Without it being Recognized Machine will not complete post. If machine is completing POST and not making any beep codes or blinking power LED ,there should not be an issue with the setup you are looking for.  You can plug your external monitor. use windows + P shortcut to switch to second display.  Please make a note that you are just telling windows to use second display when it boot. You will still not able to access BIOS(F2) or one time boot menu (F12) it will still appear on broken LCD.       
  I had encountered about 9 months ago the problem related to my laptop “Dell Inspiron 15-7559” LCD-matrix severe damage, due to which my laptop displays almost nothing. Now and only now (NOT BEFORE), because of some hard circumstances (such as severe form of СOVID-19 disease treatment), I’ve decided to attempt to solve the foresaid problem with minimal cost, WITHOUT using pretty expensive services (to me) related to LCD-matrix replacement – to connect my laptop to the old VGA port monitor via a HDMI-TO-VGA adapter and to use the monitor as the main video-output device. Thus I would like to know, in case if it’s possible and does make sense, an EXACT method of connecting a video-output device to a Dell laptop of the foresaid model and activating a video-output device for its successful work, a method of setting up my old monitor as the main output device “in blind way” (if you please) via laptop BIOS of my current version. Unfortunately, my current concrete BIOS version is unclear, the only thing regarding my BIOS version I know is the BIOS version seems to be either the one, which has been released before the laptop purchase (February, 2017), the old one, or the updated in 2020 – 2021 version, by the period of my laptop display breakdown. In case if you would like or have to ask any relevant to this subject question, you’re welcome. Thanks for any help or meaningful feedback from you in advance.
Connection of Dell Inspiron 15-7559 laptop with broken LCD to an old VGA monitor