Chrome OS will soon support external display size adjustment options for people who have an external display connected to their Chromebook. The new setting, which is currently being worked on by the Chrome OS team, will be found in the settings menu under the display settings sub-menu, and after users click on the separate tab which shows up if an external display is connected. On this tab, the display size option will be sitting under the options for display resolution, and a little slider bar next to it will let the user modify the display size to show larger content. It isn't made clear what percentage the slider goes up to, but the image below shows that it starts at 150-percent.
The idea behind this is to allow for content to be shown with a clear and sharp picture quality so users have the best experience possible when using their laptops, even if the integrated screen is not the screen that they're using. Right now this isn't an option which has been rolled out to all Chromebooks and there's no mention of when the option will hit the stable version of Chrome OS, but it is possible to enable the display size adjustment for anyone who wishes to check it out before Google makes it a permanent feature.
To get to it, users will first have to toggle on the "enable display zoom settings" flag. This is an experimental flag so by enabling it the option will become available but it should be noted that there is a possibility of things not working quite as intended, and it's likely that it will stay that way until more development work is done with it and Google rolls it out completely. The other caveat is that to enable this experimental Chrome flag you have to have your Chromebook operating on the Chrome OS Dev Channel, which some users may not be inclined to do. This also means that it will still have to go through the Beta Channel before it makes its way to the Stable build of Chrome OS, which could still be further out than expected. If you're keen to test this out, make sure to move your Chromebook over to the Dev Channel and then navigate your browser to chrome://flags/#enable-display-zoom-setting to hit the toggle, then simply reboot the browser and you should have the option to adjust the slider.