Oh my God! This happens to me too!
I had no idea it could be fixed that way. However, there is no such “Customize” option in either my Edit or Window menus…
In that case go to Windows > Workspace > Select Layout. I had another user, two days ago, saying that some menu commands went missing when the layout changed without help from the user. The Ghost in the machine and all that.
Once you get the desired layout back and all is well either press F4 or Windows > Workspace > Save Layout as…and save your layout with a more memorable name. My memory is fairly bad these days (yep getting old) so I did this early on once I got my Layout how I wanted it. Plus it is customised so saving it made sense too.