PlaceholderRename.py

def matchPlaceholderName():
	# Function to rename placeholder to match the category name 
	# Select props collection
	placeholderString = "Placeholder"
	propsColl = bpy.context.collection
	categoryArray = []
	placeholderArray = []
	placeholderCollection = bpy.data.collections[placeholderString]
	if (propsColl.name == "Props"):
		# Fill both array
		for p in placeholderCollection.children:
			placeholderArray.append(p)
		for c in propsColl.children:
			categoryArray.append(c)
	for p in range (len(placeholderArray)):
		catName = categoryArray[p].name
		placeholderArray[p].name = "PH_" + catName