Thank you for having this question because it allows me to be able to solve problem in command line now, because it already happens to do that with my Dell XPS 13
you can identify the resolutions of your screens with xrandr with the flag q
$ xrandr -q
Exemple with one monitor
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
Based on answer
you can use gtf height width refresh_rate and get an new modeline as response and then you can create new mode with the output of the first command xrandr --newmode modeline, after that you need to ensure in which output you want to set up the modeline, you can check this with xrandr -q after get the response add the newmode to the desired ...
I use VirtualBox almost daily. I have a MacBook Pro with Elementary OS 5.0 and the screen resizes just fine. I had two hoops to jump through first:
Add the Extension Pack
a. Launch VirtualBox. Go to Help -> About VirtualBox. Make a note about the version.
b. Go to the VirtualBox website. Click on Downloads.
c. If your version of VirtualBox is not ...