One of the big problems with Zoho Inventory is that it does not have multi-select lookup fields. Here's the use case. Say we have a wholesale company that wants to distribute products across some store chains. Think about each chain as a sales channel with its unique set of products. Therefore, we need to indicate at the item record level that the item is allowed to be sold to the particular chain(s). Ideally, we create a custom module where we list the chains and a multi-select lookup field at the item level where we set the relationship between an item and the chains. 

But it is impossible due to the following reasons:

1) Custom modules in Zoho Inventory cannot be accessed through its API. At least, this is what the support team told us.

2) There is no such thing as the multi-select lookup field. It does exist in CRM but not in Zoho Inventory.

Even if we use some Customer record as a parent account for the whole chain, thus avoiding the custom modules, it does not improve things because we can't establish the relationship between a single item record and multiple customer records. Yes, there is a non-lookup multi-select custom field, but it also has problems because for some reasons it cannot be used as a filter in the Custom Views, making the user experience miserable.