Show all logged In users in the interface.

I do not know of a way to do that. What is your use case?

Hello thiliniu0001, is this a portal or site? Since you are using the word logged in users, I am assuming that it is a Site. In case of Site the answer is no, we do not have an option as of now. But if it is a portal may be I can suggest some ideas.

I think you are looking for a list of all the logged-in user to the environment, I am not sure it is available OOTB. You might have to play with kdb files.

I needed something similar and created a constant for all users, then used an expression rule with a!forEach. There may be an easier way but this worked for what I needed. 

a!forEach(
items:getdistinctusers(cons!GET_ALL_USERS_POINTER),
expression: fv!item & ":" &
user(fv!item,"firstName")& ":" &
user(fv!item,"lastName")& ":" &
user(fv!item,"email")& ":" &
user(fv!item, "status")
)

There are 2 Functions which are available like queryappianlogs() or readlog() which can help you get the data into the interface and can show the data in the screen.

Alternatively, you can write a plugin which does the same thing as per your specification.