Steps to repro: Open the Project Wide Actions window -> Create the ProjectWideActions asset and select one of the actions in the list -> deselect the window ->Observe that your selection is reset

Similar if not the same issue as: [https://jira.unity3d.com/browse/ISX-1630] that is still present in current 1.8.2/1.8.3 versions

Alternative steps that are more common: You can use this project from here: https://jira.unity3d.com/browse/ISXB-505 - > Open an input actions asset -> make sure auto save is on and you have a binding to edit -> edit it once and try to open the binding path dropdown again -> selection is dropped and a save is prompted