In eclipse workbench in Import view there are some pre-defined menu items, which are:
Supplied Implementation:
The workbench comes preloaded with the basic import engines for files and directories.
Here they are:

The question is: is it possible to remove them from Import view? Can it be done not by code but by changing some plugin.xml configuration files?
You may find an answer in this possible duplicate question: How to remove a Category from Import wizard in Eclipse-RCP?
BTW: If you are investigating that deeper, please note that the extension point is called “activities”, but that functionality is always referred to as “capabilities” in Eclipse terminology.