Those @ABC are basically just row references within text. When you hover on row references you get the popups with all the visible fields from the relevant base table.
So if you have a table e.g. Tasks with button columns visible and displayed as the first ones, you can do
Tasks.Filter(...).BulletedList()
and get your list of row references.
Don’t confuse with
Tasks.Filter(...).Name.BulletedList()
where you’d get a list of task names (text values), not row references to the tasks themselves.
You can also go full crazy mode and construct these popups formulaically using black magic
(from here)
But that’s for the ascended ones.