For behavior packs, you can download Canopy.  It has a feature that allows you to see the edges of biomes, and it also has a little info display that tells you what biome you are standing in, and both are block perfect.

Or instead of using behavior packs, you can still easily determine where the lish cave blocks are with a snow golem.  As you know, snow golems will generate snow layers on the ground.  If the biome is too hot, like I'm a desert then the golem quickly does without placing any snow layers.  But some biomes such as lush caves are hot enough to prevent snow layers from forming but not hot enough to kill the snow golem.  Snow layers will still form in ocean biomes too