scale display without decreasing resolution on external monitor

Our apologies for any confusion yarden92. 

Adjusting the resolution in System Preferences > Displays as you’ve been doing would adjust the text size, along with the windows and other content as it appears on the display. Utilizing accessibility features such as Zoom may provide the best result in viewing larger text on your Mac without adjusting the resolution. You can adjust Zoom settings in System Preferences > Accessibility, then click Zoom in the left column. Once you click on Zoom you can check Enable Hover Text, which can enlarge text and other content when the pointer is moved over that area. You can customize how Enable Hover Text by click Options to the right of that feature. More information about Zoom and changing Zoom advanced options can be found in the following article. 

Change Zoom advanced options for accessibility on Mac

You'll also find additional information on how Zoom works, and the best features of Zoom that works best for you in that article.

Apple does appreciate our feedback about their products, services, and features also. If you would like to provide feedback to Apple, you can do so via the Product Feedback website. 

Take care!

Hello yarden92,

It sounds as though you’re wanting to adjust the text size on an external display. You’ve come to a wonderful place for help! 

Adjusting the resolution is a great way to adjust how the Desktop and applications appear on the external display. In addition to those steps, you may find accessibility features beneficial for increasing text size, or getting the Desktop to appear as you desire on the external display. You can find helpful information about accessibility shortcuts and features via the following links. 

Mac accessibility shortcuts

Use the Accessibility Options panel on Mac

Take care!