In combat, the GUI features a status effect panel that is meant to show all the effects that are altering your units' stats. However, several common status effects don't appear on it. The following are notably absent:

• The Bark Skin buff used by Wild Walker Agache Shaman
• The Vaccination buff used by Necrophage Proliferators
• The Increased Fire buff used by Ardent Mage heroes
• The Mark of the Predator debuff used by Forgotten Predatores
• The Stun debuff

To save you some time, I made a mod that fixes all of this. It's on the Steam workshop here.