It seems this is only an issue when using collapsed topic format in the course. I have tested other course formats and the option is available to copy to sharing cart. I checked in version 3.6 and the option is available when using Sharing Cart. So it looks like this is something that began with the 3.7 version update. You can copy the individual items in the section. You can also copy the entire section if you are using topics format or weekly format. Here is a screen cast of the issue https://www.screencast.com/t/ElRC7IPta and https://www.screencast.com/t/TQUddCsKDV

STEPS TO REPLICATE
Ensure Sharing Cart is enabled on site
-Log onto the site.
Navigate to Site Admin Plugin-Blocks- Manage Blocks
-Navigate the blocks to find Sharing Cart
-If Sharing Cart is not found, it will need to be enabled in the Control Panel

Add the Sharing Cart block to course
-Navigate to a course
-If using Boost or Classic theme, click the turn on editing option
-From the course home page, scroll to find the option to add Add Block to course
-From the drop down select Sharing Cart

In the course

• Navigate to Course Admin- Edit Settings
• Under the Course Format section, select Collapsed Topics
• Save Changes
• Add topics to the course by selecting the plus sign under the main topic
• Once the topics have been added, refresh your browser page.
• Now select the edit menu drop down option next to the topic heading, there is no option to copy to sharing cart