RE: Can I edit the Add New Activity List in Top Navigation
Hi Lori,
You should only see these options by default for the top bar:

If you see other options, these have been added with customizations (by you, an ISV add-on that you installed, from a partner, etc.)
Now in the out-of-the-box Quick Create (the + icon), you can choose what activities are available (in the screenshot below, Visit Report is a custom entiy).
