When trying to add custom models, adding blocks makes sense. You add the models to the folder custom_blocks/blocks/models.

But when adding custom item models, you have to add them to custom_blocks/blocks/item_models, which just doesn't make sense.

Also these folders do not generate on their own. It would be nice to have these auto generate.

I must have been very tired while implementing that feature. I will fix it as soon as I can.

What version of minecraft were you playing with

The directory items/models does exist for items that do not have a block associated with them. For block item models, blocks/item_models exists.