We can make an article visible for specific customers by creating a new "User Group" to add some specific customers into that newly created "User Group" and changing the KB section visibility to newly created "User Group"

1.1 Go to "Setup" ---> Select "Help Center" from "Channels"

1.2 Tap on "User Groups"

1.3 Tap on the button "Add Group"

1.4 Give a name for newly creating group

1.5 Tap on "Add Users"

1.6 Select the user to add in the group and tap on "Add " button

1.7 Users are added successfully into the group

2.1 Tap on "Manage" from KB page

2.2 Select "Organize"

2.3 Tap on "Edit" from the section which you are using in the portal

2.4 Select "Groups" from "Visibility"

2.5 Tap on the button "Continue"

2.6 Select the "Newly created Group" and tap on "Add" button

2.7 Tap on "Update" button to save the changes you made

3.1 Select the Article which you want to change its visibility

3.2 Tap on "Category"

3.3 Choose "Department" from "Category" which you added "Account" group as its visibility