The point of it
The idea (from Paul Raper) is to be able to follow up a collocate by requesting a new concordance based on it, in the same text files as selected for the collocate. This aids exploration of related words.
How to do it
Here is an example, where there is a collocate list relating to KISS.
Select a word of interest, such as HAND,and select double-click in the Total column. (That tells Concord you wan to follow up the cases where HAND is a collocate of KISS.)
You get offered a choice:
Choose Show to re-order your existing concordance lines so those with HAND float to the top:
or Compute: