title: Merging Columns with separator ',' and don't render separator if no value exist
body: <p>I'm merging data into column A like this:  </p>
  
  <p>=B2&amp;","&amp;C2&amp;","&amp;D2   </p>
  
  <pre><code>A        |  B | C  | D 
  ES,,        ES      
  DE,NL,IT    DE  NL  IT
  CH,,        CH      
  CH,,        CH      
  DE,BE,AT    DE  BE  AT
  FR,BE,      FR  BE  
  CH,SG,      CH  SG  
  AT,CH,ES    AT  CH  ES
  </code></pre>
  
  <p>Yet, if there are no values in a column it appends e.g. extra  ,,  what I don't want. So result should be like </p>
  
  <pre><code>A        |  B | C  | D 
  ES          ES      
  DE,NL,IT    DE  NL  IT
  CH          CH      
  CH          CH      
  DE,BE,AT    DE  BE  AT
  FR,BE       FR  BE  
  CH,SG       CH  SG  
  AT,CH,ES    AT  CH  ES
  </code></pre>
  
  <p>How to do so? </p>