If you want a separate form for adding categories, you can use this code to create them. If you want to keep the category creation inside the same form that creates posts, this custom code is not needed. Use a "Tags" field instead, and map it to your category in the "create posts" settings tab.

This example below will add the WordPress Media button to all Rich Text fields used throughout your site. Please note that the Add Media button will only appear for users who have permission to edit WordPress posts.

Use the code below to remove specific characters from a value in a filter. Change 205 to your View ID and change 84 to the ID of the field in the filter.