Copy can work on individual entries (and their descendants), on selected text and between programs.
Copy copies selected entries or text to a clipboard buffer. Paste inserts the contents of this buffer at the current cursor position. Within BrainStorm models the structure is preserved. To external programs the entries are pasted in sequence but without indents. (Reasons: we don't know whether the destination program will be able to interpret indents and, if it doesn't then removing them would be a real pain for you.)
Select a block of entries by first selecting one by clicking the mouse on the entry icon then, while holding the Shift key, click on the last entry icon in the block. Select multiple individual entries by holding Ctrl down while clicking the mouse on the entry icons. They are stored into the buffer in the sequence they are selected. This is a brilliant way to resequence entries in a list. And use Ctrl+A to select all the entries in the current list.
Select text within an entry by holding down left mouse button and dragging across text. Alternatively use Shift+arrow key. Please note that Windows uses white on blue for highlighting, if you have chosen this colour scheme, then the highlight will not contrast.Use: