Is there an official Magento 1.x Module Development Reference/Documentation?
I had been selected recently to manage and improve an ecommerce with Magento 1.9 and they asked me to build several custom attribute modules so I figured how to build the basics about, but in the install of the module, I need to know the constants that I can use in "used_in_forms" because several attributes need to be in different forms on the store, but I can't find any valid reference, just several StackOverflow/Exchange topics with fragments of code where I can find several of those constants but I need all of them...
Any help with that? or since Magento belongs to Adobe, I'll need to pay thehighly expensivecertifications? I'll appreciate.