Any animation that was naturally loaded by the engine without preloading should automatically be purged from the temp cache after a while.
To be honest, you're game seeing as it's pixel art & I'm assuming has quite a low default resolution, you shouldn't really need to bother with preloading any of your animations. Try converting your images & animations to webp format to decrease loading times & required hdd space & your game should run nice & smooth.
By episodes do you mean that you will be distributing your game in parts or are you talking about chapters in a single feature length game?
Quick tip: if you press Home (inicio) key on your keyboard while running your game via the VS editor, it will display an overlay with information about how much ram, vram & so on various different aspects of your game are using. It updates more or less in real time, so you can see what is happening when a specific script is executed or when a new animation starts, etc. Very useful.