Modify and change (not move) default columns and column titles in library header bar

I know that I can simply drag the default library column headers around to suit my choice, but how can I add/subtract/change these headers for a particular library? Thank you in advance.

You can click on the menu with the downward pointing triangle to the right of the rightmost column or Control-click on one of the column headers.

I clicked and got this drop down. I want to add items to this list - is it possible or defaulted and limited to this list?

The list of columns is fixed. Which items would you like to add?

Understand. Thank you. Will create and send if I cannot find workaround.