The reason that they are invisible is probably because they are on a ToolStripPanel (the top panel of the container) which is hidden (collapsed).

That said, you cannot edit any controls that are on the inherited base form anyway. You can only edit them in the base form, and those changes will then show up in all derived forms. That is just how inherited forms work.

I do find that, in the case of Menu/Toolstrips, this is not optimal behavior. I would like it if you could still have the option of adding items to them. I am often in a situation where I need many forms with the same layout, but other toolstrip items. I do however have an Infragistics toolset which has a new toolstrip control which I'm pretty sure is editable in inherited forms. I'm not sure how they did that, lol.