\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[siunitx,fetbodydiode,smartlabels]{circuitikz}
\usetikzlibrary{positioning}
\begin{document}
\begin{figure}
\centering
% Based on a template by Erno Pentzin (2013), http://www.texample.net/tikz/examples/ac-drive-components/; based on suggestions from tex.stackexchange, https://tex.stackexchange.com/questions/395535/some-help-with-connections-and-voltage-arrow-in-circuitikz#395561
% Based on a template by Erno Pentzin (2013), http://www.texample.net/tikz/examples/ac-drive-components/; based on suggestions from tex.stackexchange, https://tex.stackexchange.com/questions/395535/some-help-with-connections-and-voltage-arrow-in-circuitikz#395561
\begin{circuitikz}[lbl/.style = {label={[label distance=4mm]above right:#1}}] % this line defines a new style to alter the distance of labels, mosfets due to diode and transformer label
\draw
% top part of switch legs
(0,0) coordinate (s1)
to ++ (0,-0.4)
%node (mosfet1) [nigfete,below,anchor=D] {$Q_1$} % old, label distance incorrect
node (mosfet1) [nigfete,below,anchor=D,lbl=$Q_1$] {} % new, label distance ok
(mosfet1) node (mosfet3) [nigfete,right=10mm,lbl=$Q_3$] {} % This is the only variable that needs to be changed to adjust the distance from Q1/Q2 to Q3/Q4
(mosfet1.S) to [short,current/distance = 0.1,i=$i_{Q,1}$,-*] ++ (0,-0.4) coordinate (t1)
% transformer
(t1 -| mosfet3.S) coordinate (hilf1) % Connect Q1 with Q3S which is electrically wrong, but easier to draw
node (T) [opacity=0,transformer core,below right=0mm and 17mm]{} % This is the only variable that needs to be changed to adjust the distance from Transformer T from node t1 (underneath Q1)
(T.base) node[label={[opacity=0]above:$N_1\quad N_2$}]{}
node[circ] (E) at ($(T.A1)+(0.35,-0.35)$) {} % Wicklungssinn T
node[circ] (F) at ($(T.B1)+(-0.35,-0.35)$) {} % Wicklungssinn T
% bottom part of switch legs
(mosfet3.S |- T.A2) coordinate (t2) % likewise counter intuitive
to ++ (0,-0.4)
node (mosfet4) [nigfete,below,anchor=D,lbl=$Q_4$] {}
(t1 |- mosfet4.D) node (mosfet2) [nigfete,below,anchor=D,lbl=$Q_2$] {}
% connection lines origins at transformer
%(T.A1) to (t1) % old, replaced by short b/c current arrows, see below
(t1) to [short,current/distance = 1,i=$i_1$] (T.A1)
(T.A2) to [short,-*] (t2)
(T.B1) to [short] ++ (0.5,0) coordinate (t3)
Du kannst jede node mit
opacity=0
ausblenden, z.B.node (T) [opacity=0,transformer core,below right=0mm and 17mm]{}
@Murmeltier: Ich denke, das könnte durchaus bereits eine Antwort sein.