Click the link "Using Software Explorer" to open help which explains how the feature works. For more info see the link
hereDon't be concerned about programs identified as "not yet classified" as long as you know what they are. There are a lot of programs that MS throws into this category like NOD32 anti-virus. Even though a program may be listed as "not yet classified", Defender does not interfere with it running. However, under Startup Programs you can choose to Remove or Diasable. Under Currently Running Programs you can end a task or open Task Manager to do the same.
Although Software Explorer provides some useful information, it is not one of the better features of Defender so I seldom use it.