It'd be great if hovering over the "Concentration Saving Throw" text showed a pop up with the definition of a Concentration Saving Throw. Hovering over the "failed" should tell you what you rolled and what the DC is. Actually, on second thought, the roll should be a separate line in the combat log!!!
- Shadowheart rolled a 3 against DC 10: fail (hover over the 3 to see exact d20 roll and bonuses)
- Shadowheart failed a Concentration Saving Throw (hover over the underlined to see the rules regarding concentration STs)
- Shadowheart lost concentration on Shadowheart
...
Also, "Constitution modifiers"??? Why is it plural?! Either 2 is your constitution mod (singular) and there should be no "s," or you have multiple bonuses to constitution (e.g., modifier plus bless) and the combat log should list and label all of those separately.