Hide / Unhide selected with children questions

i made a simple add-on to hide/unhide select object and children on the view port and renderer. See here (Files · main · Philippe Van Hecke / Blender Hideunhide All · GitLab) but have two issues.

First one is that I would like to put operator under the Show/Hide submenu and don’t know how to do it. Now it is located at the end of the Object menu.

The second one is a litle bit more tricky, because when hiding object and children in view port it was not selected anymore. So I would like to know in bpy how to get information about selected item in the outliner.

Kr Philippe