WhatIsThat? allows you to see the Block/Entity you are looking at in your bossbar (or action bar) along with some other information about it (Entity health, Villager Profession, Items in chest and more). The plugin also integrates with many plugins (like ItemsAdder, Nexo, Minetorio, Slimefun) to properly display their blocks/entities.

the plugin supports:
ItemsAdder-Moving
EliteMobs-Moving
AuraMobs-Moving
AuraSkills-Moving
Minetorio-Moved
Valhalla MMO-Moving
Slimefun-Moving
LiteFarm-Moving
Nexo-Moving
if you want compatibility for a plugin or more features for a plugin compat, make a issue in the Github.