Typo in "BaseEditorSettings.ini": under section [/Script/UnrealEd.ContentBrowserSettings], key "DisplayPluginFolder" (singular) should read "DisplayPluginFolders" (plural).

File "<ENGINE_PATH>/Engine/Config/BaseEditorSettings.ini" contains the following setting:

[/Script/UnrealEd.ContentBrowserSettings]
; Whether to display the game project plugins in the Content Browser
DisplayPluginFolder=True

However, the definition of class UContentBrowserSettings in file "<ENGINE_PATH>\Engine\Source\Editor\UnrealEd\Classes\Settings\ContentBrowserSettings.h" contains:

UCLASS(config=EditorSettings, MinimalAPI)
class UContentBrowserSettings : public UObject

{ /** List of plugin folders to display in the content browser. */ UPROPERTY(config) bool DisplayPluginFolders; }

Note that the name on the INI file does not match the name in the configured class, which means that this setting has always been ignored until now (so the fix might be correcting the typo or removing the line entirely). This affects, for example, the SPathPicker/SPathView widgets that get created by the Struct Customization of properties with type FDirectoryPath (see "Steps to Reproduce").

Also, perhaps this setting should appear in the "Editor Preferences" dialog (not part of the fix for this bug). Currently, it can be changed in-Editor only by clicking the settings icon in a Content Browser tab and changing the state of "Plugin Content", which supposedly refers to the per-Content-Browser-instance setting (struct FContentBrowserInstanceConfig inside class UContentBrowserConfig), not to the Editor-global setting (class UContentBrowserSettings). Interestingly, changing the state of "Plugin Content" in this manner affects both the per-instance and the editor-global settings.

 

1. Edit file "<%LOCALAPPDATA%>/UnrealEngine/<VERSION>/Saved/Config/WindowsEditor/EditorSettings.ini". Under section [/Script/UnrealEd.ContentBrowserSettings], make sure there is NOT a line "DisplayPluginFolders=True". This line does not exist on a fresh engine installation, but it gets added when the user clicks the Settings icon in a Content Browser tab and changes the state of "Plugin Content"

2. Edit file "<ENGINE_PATH>/Engine/Config/BaseEditorSettings.ini". Under section [/Script/UnrealEd.ContentBrowserSettings], verify that there is a line "DisplayPluginFolder=True" (singular, not plural).

3. On a UE project, implement the following C++ actor class:

UCLASS()
class AMyActor : public AActor
{
GENERATED_BODY()
public:
UPROPERTY(EditAnywhere, meta = (LongPackageName))
FDirectoryPath MyDirectoryPath;
};

4. Open the project, make sure there is at least one active project plugin. If necessary, create a Content-only plugin (Edit – Plugins – Add – Content Only – Create Plugin).
5. Create and edit a blueprint derived from AMyActor
6. On the "Class Defaults" tab, click the three dots next to property "My Directory Path". Note that the "Plugins" folder does not appear.
7. Correct the typo on file "BaseEditorSettings.ini"
8. Restart the Editor
9. Repeat step 6 and note that the "Plugins" folder does appear.