Are there shortcuts for text editors/processors to delete the rest of a line?

"Delete to end of line"

Windows, try this:
Hold SHIFT and hit End (selects the text) then Delete.

Linux, some editors mimick (i.e. 'works' the same as) windows editors, "native editors" (especially those running in shell/terminal) e.g. nano (pico) usually differ:
First press ENTER to split the line, creating a new line with the end part of the previous, then hold CTRL and hit k to kill the line.

In Vim, D in normal mode will delete to the end of the current line.

Delete to end of line

In Notepad++ it is the following shortcut:

CtrlShiftDelete Delete to end of line

Source: Notepad++ Keyboard Shortcuts - Virendra's Techtalk