When using the Web Inspector as an undocked window it is important to understand that the Web Inspector is opened as an external window, opened outside the context of 4D's MDI window.

Clicking on the 4D application after opening the Web Inspector as an undocked window will bring to front the 4D application window, this operation may cover up the external Web Inspector if the two windows overlap.

To overcome this, move the Web Inspector away from 4D so they do not overlap; such as moving the Web Inspector to a secondary monitor and have the 4D application on the primary monitor. Doing this will allow you to view both 4D and the Web Inspector at the same time.