Is it possible to map Alt + Arrow Key to the start and end of a line in various applications?
You can use Autohotkey and following script:
!Left::Send, {Home}
!Right::Send, {End}
!+Left::Send, {Shift down}{Home}{Shift up}
!+Right::Send, {Shift down}{End}{Shift up}
Last two lines make work selection like home\end + shift!