Hi! So, loving the mod so far, but quick question: 

At Colosso I want to use my party to cheer on Isaac but I can't get one of them to get overworld Growth (now named Sprout). Garret has it but he needs to use Move in another booth. Also, Djinn don't give overworld Growth anymore.

I know equipping the Sappling Sword provides it but most equipment gets removed as you enter the arena. Exceptions are items for overworld psys like Force Orb and Douse Ring (i think it's called?) and Casual/Brutal keys. 

So what are my solutions? Cheers and thanks for the mod!

The intended solution is to get the Sprout Clover, which becomes obtainable as an item artifact once you sell the Sapling Sword. It's an Overworld item, like the Force Orb, so it will carry over into Colosso.  If you can't find it go to the item lady where you would normally buy items like Clarity Clovers, but choose "artifacts".

Glad you're enjoying the mod. This does open my eyes to the fact that Sprout is not nearly as accessible as I intended to be and will see what I can do to alleviate that once version 2 is released.