SentryOne Plan Explorer properties window
If you right-click on the column header on any of the grids, there is an option called Column Chooser:


  


This exposes a panel that lists all the columns that are available in that grid. You can drag any of these onto any location in the grid. Here is an example from Top Operations, where both Predicate and Seek Predicates are available:


  


The really nice thing about the grids is that all operators are listed together. In SSMS, to compare some of the more obscure properties between two operators, you either have to flip between tooltips and/or properties panels, or take screen shots (ugh).

If you post your plan somewhere and describe which index seek you mean, I can show you how to make these properties front and center.