Hi Michael, I have added a category import function under the Global Options > Import / Export Links tab. You will find it by updating to version 7.5.1.
A template for the CSV format is provided in the plugin’s base directory (also linked in user interface). It is called catimporttemplate.csv. You can specify for the categories to be top-level categories by leaving the parent field empty, or specify the name of a parent category.
Let me know if this works as expected or if you encounter any issues. You can find the donation link for Link Library here: https://ylefebvre.github.io/wordpress-plugins/link-library/. Thanks in advance for your support!