Sloth
Mac app that shows all open files, directories, sockets, pipes, etc.
... of the lsof command line tool. The output is parsed and shown in a searchable, filterable outline view with all sorts of convenient additional functionality. Sloth is free, open source software and now has a home on GitHub. It has been continuously developed and maintained for a very long time (since 2004). Inspection window with detailed macOS and Unix file/socket/process info.