Since march version (2.67.5404.581) it's no longer possible to select a relationship directly in the relationship view. Earlier this enabled users to quickly identify the columns that were used for this relationship in both tables connected. This was done by Power BI highlighting the columns in each table.
This is no longer possible in the same way. For example if you have a table with a long list of columns where you earlier could select the specific relationship and scroll to find the highlighted columns on each side (which were a part of the relationship).
In the new march update for PBI Desktop you need to either open the "Manage relationship" view or open the relationship editor and then scroll sideways on each table to see the columns used in the relationship, which is not as intiutive.