Xrfgtjtk

The following code

documentclass[tikz,border=1mm]{standalone}

    usepackage{tikz}

    begin{document}   

    newcommand{opacity}{0.6}      

        begin{tikzpicture}                             

        draw[xshift=1cm,fill=gray,draw=black,opacity=opacity] 

        (0,0) -- (3,3) -- (3.2,3) -- (0.2,0) -- (0,0);

        draw[xshift=2cm,fill=gray,draw=black,opacity=opacity] 

        (0,0) -- (2,2) -- (2.2,2) -- (0.2,0) -- (0,0);  

        draw[xshift=3cm,fill=gray,draw=black,opacity=opacity] 

        (0,0) -- (1,1) -- (1.2,1) -- (0.2,0) -- (0,0);        

        end{tikzpicture}      

    end{document}

produces the following output:

How can I connect the edges of the rectangles with a line? I don't want to use coordinates (draw (0,0) -- (2,2)) but rather something like

draw (rectangle1.north east) -- (rectangle2.north west).

It would also be great if there is a solution like:

draw (A1)(0,0) -- (B1)(1,1) -- (C1)(1.2,1) -- (D1)(0.2,0) -- (E1)(0,0);

draw (A2)(0,0) -- (B2)(1,1) -- (C2)(1.2,1) -- (D2)(0.2,0) -- (E2)(0,0);

draw (A1) -- (C2)

Something like this ?

documentclass[tikz,border=1mm]{standalone}

    usepackage{tikz}

    begin{document}   

    newcommand{opacity}{0.6}      

        begin{tikzpicture}                             

        draw[xshift=1cm,fill=gray,draw=black,opacity=opacity] 

        (0,0)coordinate(A1) -- (3,3)coordinate(A2) -- (3.2,3)coordinate(A3) -- (0.2,0) coordinate(A4) -- cycle;

        draw[xshift=2cm,fill=gray,draw=black,opacity=opacity] 

        (0,0)coordinate(B1) -- (2,2)coordinate(B2) -- (2.2,2)coordinate(B3) -- (0.2,0)coordinate(B4) -- cycle;  

        draw[xshift=3cm,fill=gray,draw=black,opacity=opacity] 

        (0,0)coordinate(C1) -- (1,1) coordinate(C2)-- (1.2,1)coordinate(C3) -- (0.2,0)coordinate(C4) -- cycle; 



        draw(A4)--(B1);

        draw(B4)--(C1);

        draw(A3)--(B3)--(C3);



        end{tikzpicture}      

    end{document}

Update using a foreach loop:

documentclass[tikz,border=1mm]{standalone}

    usepackage{tikz}

    begin{document}   

    newcommand{opacity}{0.6}      

        begin{tikzpicture}



        foreach xs/p/x in{1/A/3,2/B/2,3/C/1}

        {draw[xshift=xs cm,fill=gray,draw=black,opacity=opacity]

        (0,0)coordinate(p1)

        --(x,x)coordinate(p2)

        --(x+0.2,x)coordinate(p3)

        --(0.2,0)coordinate(p4)

        --cycle;}



   draw(A4)--(B1);

   draw(B4)--(C1);

   draw(A3)--(B3)--(C3);



        end{tikzpicture}      

    end{document}

As far as I understand your post, if two coordinates are given, the full shape is fixed. Your shape is not a rectangle, but a trapezium, and there are predefined shapes available.

documentclass[tikz,border=3.14mm]{standalone}

usetikzlibrary{shapes.geometric}

begin{document}

begin{tikzpicture}[my trapez/.style={trapezium,%inner xsep=0pt,inner ysep=0pt,

trapezium left angle=135, trapezium right angle=45,rotate=45,

minimum width={#1*sqrt(2)*1cm},minimum height={sqrt(2)*1mm},draw,fill=gray,

 trapezium stretches body,anchor=west}]

node[my trapez=3]  (L)    at (1,0) {};

node[my trapez=2]  (M)    at (2,0) {};

node[my trapez=1]  (R)    at (3,0) {};

draw ([xshift=-sqrt(2)*1mm]L.west) -- ([xshift=sqrt(2)*1mm]R.west); 

draw ([xshift=sqrt(2)*1mm]L.east) -- ([xshift=sqrt(2)*1mm]R.east); 

end{tikzpicture}

end{document}

As you can see, there are two mild problems with this approach:

1. it is nontrivial to control the dimensions precisely, at least for this shape;


2. to specify the position precisely, you need to think a bit. (This is also the case in Zarko's otherwise nice answer.)

Therefore, I'd like to propose a different route, in which you to draw and fill the thing as a decoration, which also lets you name the coordinates.

documentclass[tikz,border=1mm]{standalone}

usetikzlibrary{decorations.pathreplacing}

tikzset{trapez width/.initial=0.2cm,

my trapez/.style={decorate,decoration={

show path construction,

lineto code={filldraw

(tikzinputsegmentfirst) coordinate(#1-south west) 

-- (tikzinputsegmentlast) coordinate(#1-north west)

-- ([xshift=pgfkeysvalueof{/tikz/trapez width}]tikzinputsegmentlast)

coordinate(#1-north east)

-- ([xshift=pgfkeysvalueof{/tikz/trapez width}]tikzinputsegmentfirst)

coordinate(#1-south east) -- cycle;

}}}}



begin{document}   

  begin{tikzpicture}

   begin{scope}[fill=gray,opacity=0.6]

    draw[my trapez=L] (1,0) -- (4,3);

    draw[my trapez=M] (2,0) -- (4,2);

    draw[my trapez=R] (3,0) -- (4,1);

   end{scope}

   draw (L-north east) --  (R-north east)

   (L-south west) --    (R-south east);

    end{tikzpicture}      

end{document}

Now you really only need to specify two coordinates, which will become precisely named coordinates.

let me elaborate my comment:

• for shapes, which you draw as you show in your mwe, this is not possible


• those shapes haven't defined names nor anchors.


• 
  

  you can do this by use of coordinates for each shape corner, but this can result in quite complex code. for example for the first shape:

  
  
  

  draw[myshape] (0,0) coordinate (A1) -- 
  
                 (3,3) coordinate (A2) -- 
  
                 (3.2,3) coordinate (A3) -- 
  
                 (0.2,0) coordinate (A4) -- cycle; 
  
  

  
  
  

  and than draw for example

  
  
  

  draw (A1) -- (A3);
  
  

  
  


• 
  

  a way to simplify this code extension can be use of the small pictures: pic (for details about it see chapter 18 Pics: Small Pictures on Paths in Tikz & PGF manual, v 3.0.1a, page 251):

  
  
  

  documentclass[tikz,border=3mm]{standalone}
  
  
  
  begin{document}
  
      begin{tikzpicture}[
  
  pics/myshape/.style = {code={ % definition of your shape
  
      draw[fill=gray,opacity=opacity]
  
          ( 0.0,0) coordinate (-1) -- ++  % south west
  
          ( 0.2,0) coordinate (-2) -- ++  % south east
  
          (#1,#1)  coordinate (-3) -- ++  % north east, coordinate is determined by parameter #1
  
          (-0.2,0) coordinate (-4) --     % north west
  
          cycle;}}
  
                         ]
  
  defopacity{0.6}
  
  pic (A) [above right] at (0,0) {myshape={3}}; % "3" is parameter which define size of shape
  
  pic (B) [above right] at (1,0) {myshape={2}};
  
  pic (C) [above right] at (2,0) {myshape={1}};
  
  draw[very thin, red, densely dashed]
  
      (A-3) -- (B-3); % instead of draw (rectangle1.north east) -- (rectangle2.north west).
  
      end{tikzpicture}
  
  end{document}
  
  

  
  



• for coordinates name you can select more meaningful names. for example instead of -1 may be more appropriate -sw, which can associate you on "south west", etc.