To bulk upload categories for the storefront you can utilize the bulk uploader.
action=add, cid, title, category1
cid should be left blank so the system generates an automatic cid (category ID), but it must be present to trigger a category upload.
title - the name/title of the category
category 1 - for master categories, this is the same as the category title
navtitle - this will be the title shown on the website navigation bar, if not included, it is assumed to be the same as title.
navdisplay - boolean that decides if the category will be displayed on the website navigation bar (1 for yes, 0 for no).
navorder - integer that determines if what order the categories will be displayed in - it assumes sequential order if this is left blank. 0 is the lowest possible value in navorder.
category 2,3,4,5 - if adding sub categories, you will need these. Category 1 will be filled with the title of the parent category and then the title of the sub category should be placed in category2... follow this path further for sub-subcategories and beyond.
Attached is an example of a successful bulk upload of 1000+ categories in a single file. With Parent Categories and Subcategories.