Search for a name using the search function on the Guest list tab.
You can visually check if the guest has any additional Plus 1's guests. This is represented on the right hand side of the searched name listing by a figure.
Example of guest with two unchecked Plus 1's: (0/2)
Tap the guest name to access their profile.
Toggle the Plus 1 + button icon to admit the additional guests one by one.
Select the back arrow top left to return to the guest list.