Secondary display Lightroom classic closes automatically after a few seconds

Hello, 

when I select several photos in Lightroom classic and display them in the secondary display, the secondary display closes automatically after a few seconds.

How and where can I set this so that the secondary display is shown permanently, i.e. until I close it?

Many thanks for your help.

Best regards, Bernhard

MacBock Pro Apple M2 Max
macOS Sonoma 14.4