hard line break; hard return
Computing term for a line break that is explicitly inserted and preserved, as opposed to a soft line break that may reflow.
To insert a hard line break in a word processor, press Shift+Enter.
改行 is a general term for any line break, while 強制改行 specifically means a hard line break that is manually inserted and preserved.
Compound of 強制 (forced) and 改行 (line break).