[Tex/LaTex] Define space between footsepline and footer

Question

How to push footer text (red rectangle) down from footsepline (green rectangle)? Position of the footer (as a whole) on the page is not relevant.

MWE: ( \setlength\footheight{1.5\baselineskip} is just pushing both boxes up)

\documentclass{scrbook}

\usepackage{fontspec}
\usepackage{blindtext}
\usepackage[
    footsepline=0.25pt, % to show the footwidth
]{scrlayer-scrpage}

\setlength\footheight{1.5\baselineskip}

\begin{document}

\blindtext

\end{document}

Answer 1

Either you shift the layers with lines up

\documentclass{scrbook}
\usepackage{blindtext}

\usepackage[
    footsepline=0.25pt, % to show the footwidth
]{scrlayer-scrpage}

% shift lines up:
\ModifyLayer[addvoffset=-.6ex]{scrheadings.foot.above.line}
\ModifyLayer[addvoffset=-.6ex]{plain.scrheadings.foot.above.line}

\begin{document}
\blindtext
\end{document}

or the layers with the foot down

\documentclass{scrbook}
\usepackage{blindtext}

\usepackage[
    footsepline=0.25pt, % to show the footwidth
]{scrlayer-scrpage}

% shift foot down
\ModifyLayer[addvoffset=.6ex]{scrheadings.foot.odd}
\ModifyLayer[addvoffset=.6ex]{scrheadings.foot.even}
\ModifyLayer[addvoffset=.6ex]{scrheadings.foot.oneside}
\ModifyLayer[addvoffset=.6ex]{plain.scrheadings.foot.odd}
\ModifyLayer[addvoffset=.6ex]{plain.scrheadings.foot.even}
\ModifyLayer[addvoffset=.6ex]{plain.scrheadings.foot.oneside}

\begin{document}
\blindtext
\end{document}