Hi @GYAN,
You don't want to open the "lvgl_guider" example project with GUI Guider. This example project is just a template for any LVGL/GUI Guider project, in MCUXpresso.
What you want to do is have the "lvgl_guider" project in the IDE, then separately create a GUI Guider project for the same board/MCU, and once you are done creating your GUI, override the "custom" and "generated" folders from the GUI Guider project with the template "lvgl_guider" MCUXpresso project.

In other words, you are just passing the actual GUI that you created in GUI Guider to a 'base' or 'template' project in MCUXpresso.
BR,
Edwin.