Overview
Once you have the list of all issues from your selected filter and selected columns displayed, you will notice that at the very left of each row there are circles with numbers in it.
These show you the number of issues connected to each task. The colors display the issue category:
Details for the linked issues
There are two ways to further investigate the linked issues:
Click on each number to see only the issues from this category listed below.
Click on the arrow at the beginning of each row to see all linked issues and their details.