After thorough internal fixes plus correcting both Add-on APIs and hooks to enable support for D, C#, and Visual Basic are finally available in Add-on API 4.0 Preview 5 and later. You can view what hooks are available via looking in UnitTestHook__ Add-ons from github.
However, H-Ext 0.5.3.x are not yet ready to be release in public. We do have to maintenance our Add-ons in order to work with development build. Then ensure all Add-ons are working as intended.
P.S. It is most likely objects management will become accessible in public 0.5.3.x and later. Currently it is in experimental stage and was not thoroughly tested. Release date for 0.5.3.x are still TBA.