Using Custom Latest in mod_comprofileronline

Setting display mode to custom latest and then selecting a field in the custom latest tab seems to have no impact. it always displays username. What am I missing?

That does not determine what the module displays, but how the users displayed in it are sorted. To change what the module displays use HTML and substitutions in the "User-text" parameter. There's also additional layouts available under Advanced Options in the Layout parameter.

Thank you for your prompt reply.
I am afraid I do not understand it.
I see a drop down for "Display Mode" which impacts what is displayed. 
I see one of the selections is "custom Latest" and then I see a tab for "custom latest" where I can select the field.

I am confused that you say I have to go the html. Are you suggesting I have to make changes to the module?
I do not understand  what the "User-text" parameter refers ?

Ok I now understand what you said. I am continuing to try and get substitutions to work under user text

Ok thanks. I got it to work. Substitutions are powerful.

I'm glad you figured out how to set the user text . I would like the module to display as in Joomla 3 the lastname firstname and username for each connected member. I configured in joomla 4 exactly the same as joomla 3 but I only display the username. Can you explain what to change in user text field?

My params in Joomla 4:
Tab Module Display mode : Online users
Tab Custm Latest Field : Username (username)
Tab Advanced options Layout : default