I assume you are running on Windows. To execute an application from the command line, press Windows+R to open a 'Run' box. Then type the following and click OK:
C:\Program Files\PixInsight\bin\PixInsight.exe --ui-scaling=2
In this example, I am assuming that 2.0 is the correct scaling factor for your laptop monitor. If this is too big, you can try with 1.5 for example.
Remember that you only have to do this once. The specified scaling factor will be stored in application preferences, and will be used until you change it manually, or until you reset application settings.