press CONTROL and KEEP CONTROL PRESSED.
LEFT CLICK into a word of the FIRST TEXT LINE in which you are interested.
optionally, you may now also press cursor down, to move through the text.
LEFT CLICK into a word of the LAST TEXT LINE.
all selected lines should appear in yellow now.
RELEASE the CONTROL KEY.
the selected lines are now in your clipboard.

instant copy a single line to clipboard

Hold CONTROL+SHIFT pressed, then left-click into a line to copy the whole line instantly to the clipboard. Blanks to the left and right are stripped automatically.

copying the lines of the current screen to clipboard

Press CONTROL+INSERT.

copying the clipboard text into the find mask

Press SHIFT+INSERT to copy the first line of clipboard text into the find mask, running an instant search.

how to step through files while copying text

As long as text is marked for copy, CTRL+PAGE DOWN/UP does not jump to the next or previous file, but simply steps one page through the text. While copying text, use CTRL+HOME/END instead to jump through files.

Next chapter: Multi Window Text Operations.

Depeche View is a high speed text search tool for Windows and Linux (WINE).
Download the free Lite Edition here, which requires no installation. Just run the tool,
then load and search all text files of a folder instantly in one window.

snapshot with 8254 files loaded. the word "interface" was found 5690 times.