title: how to take multiple columns and stack them into 1 column, and make the old column names a column
body: <p>I want to take this table
  <a href="https://i.stack.imgur.com/V1si1.png" rel="nofollow noreferrer">a table with monsters and columns with skill bonus's most of them null</a></p>
  <p>|Montername|survival|stealth|...(there is like 20 columns)</p>
  <p>|abc.......|1.......|4......|</p>
  <p>and I want to quickly stack them so I only have 3 columns,</p>
  <p>|Montername|skillbonus|skill|</p>
  <p>|abc.......|1.........|Survival|</p>
  <p>|abc.......|4.........|stealth|</p>
  <p>I know I can manually pull each column as [&quot;monstername&quot;,{skill}] and then stack them with concatenate, and then remove the NaN's. Hoping for a quicker solution.</p>