Leader Lines in Callouts
Assign a curved leader.
In[1]:=

Grid[{Table[
   Plot[{Callout[.5 Sinc[.5 x], ToString[name], Automatic, 0, 
      Appearance -> name, 
      LeaderSize -> {{24, 60 \[Degree], 3}, {40, 0 \[Degree]}}], 
     Sinc[x]}, {x, -1 Pi, 4 Pi}, PlotTheme -> {"Business"}, 
    PlotRange -> All, FrameTicks -> None, 
    ImageSize -> 180], {name, {"Leader", "CurvedLeader"}}]}]Out[1]=

Specify the length of a leader.
In[2]:=

Grid[{Table[
   Plot[{Callout[.5 Sinc[.5 x], ToString[leaderLength], Automatic, 0, 
      LeaderSize -> {{leaderLength, 45 \[Degree], 0}, {20, 
         0 \[Degree]}}], Sinc[x]}, {x, -3 Pi, 3 Pi}, 
    PlotTheme -> {"Business"}, PlotRange -> All, FrameTicks -> None, 
    ImageSize -> 150], {leaderLength, {10, 20, 40}}]}]Out[2]=

Specify the length of the neck.
In[3]:=

Grid[{Table[
   Plot[{Callout[.5 Sinc[.5 x], ToString[neckLength], Automatic, 0, 
      LeaderSize -> {{10, 45 \[Degree], 3}, {neckLength, 
         0 \[Degree]}}], Sinc[x]}, {x, -3 Pi, 3 Pi}, 
    PlotTheme -> {"Business"}, PlotRange -> All, FrameTicks -> None, 
    ImageSize -> 150], {neckLength, {0, 20, 40}}]}]Out[3]=

Specify the angle of a leader.
In[4]:=

Grid[{Table[
   Plot[{Callout[.5 Sinc[.5 x], ToString[StandardForm[leaderAngle]], 
      Automatic, 0, 
      LeaderSize -> {{20, leaderAngle, 3}, {10, 0 \[Degree]}}], 
     Sinc[x]}, {x, -3 Pi, 3 Pi}, PlotTheme -> {"Business"}, 
    PlotRange -> All, FrameTicks -> None, 
    ImageSize -> 150], {leaderAngle, {45 \[Degree], 130 \[Degree], 
     270 \[Degree]}}]}]Out[4]=

Specify the angle of the neck.
In[5]:=

Grid[{Table[
   Plot[{Callout[.5 Sinc[.5 x], ToString[StandardForm[neckAngle]], 
      Automatic, 0, 
      LeaderSize -> {{10, 60 \[Degree], 3}, {25, neckAngle}}], 
     Sinc[x]}, {x, -3 Pi, 3 Pi}, PlotTheme -> {"Business"}, 
    PlotRange -> All, FrameTicks -> None, 
    ImageSize -> 150], {neckAngle, {0 \[Degree], 30 \[Degree], 
     180 \[Degree]}}]}]Out[5]=

Style the leader.
In[6]:=

Grid[{Table[
   Plot[{Callout[.5 Sinc[.5 x], ToString[StandardForm[style]], 
      Automatic, 0, 
      LeaderSize -> {{30, 45 \[Degree], 3}, {10, 0 \[Degree]}}, 
      CalloutStyle -> style], Sinc[x]}, {x, -1 Pi, 5 Pi}, 
    PlotTheme -> {"Business"}, PlotRange -> All, FrameTicks -> None, 
    ImageSize -> 150], {style, {RGBColor[0.34398, 0.49112, 0.89936], 
     AbsoluteThickness[2], AbsoluteDashing[{1, 3}]}}]}]Out[6]=

Style the knockout around the leader.
In[7]:=

Grid[{Table[
   Plot[{Callout[.5 Sinc[.5 x], Column[koStyle], Automatic, 0, 
      LeaderSize -> {{25, 45 \[Degree], 3}, {20, 0 \[Degree]}}, 
      CalloutStyle -> {Black, Directive[koStyle]}], 
     Sinc[x]}, {x, -1 Pi, 5 Pi}, PlotTheme -> {"Business"}, 
    PlotRange -> All, FrameTicks -> None, 
    ImageSize -> 
     150], {koStyle, {{GrayLevel[1], Opacity[1], 
      Thickness[.05]}, {GrayLevel[1, .6], 
      Thickness[.05]}, {Opacity[0]}}}]}]Out[7]=
