Pluginaid

Adds a dashboard widget displaying a list of users currently logged in to your site. Useful for monitoring live user activity and session management.

Logged In Users

Adds a dashboard widget showing which users are currently logged in.

jerrystewart99

An easy-to-use lightweight WordPress Plugin that can show the currently logged in user name or other metadata.
Replaces a target menu item with alternate txt which can also include usermeta. User metadata would typically include ‘first-name’, ‘last-name’, ‘nickname’ etc 
Any available usermeta may be used.
Optionally decorates the menu item with a user avatar. The avatar size is adjustable.
The target menu, the replacement text and the avatar are all set on the options menu which is found in [Settings|Logged In As]
Designed with the intention of being used in conjunction with a Membership plugin.
The website visitor must be logged in for this plugin to work
To date has been tested only with Ultimate Member and MemberPress membership plugins but others may work too

Logged In As

Tested now in Gutenberg theme but...

Show the currently logged in user name and avatar

Logged In Users vs Logged In As