I recommend that you initially build your term sets using MindJet Mind Manager. This tool allows you to easily create and modify hierarchies on the fly, and represents them in a very visual way that makes it easier for decision-makers to see options while being discussed.
Once drafted, you can export your Mind Manager hierarchy to Excel and tweak it to upload to your Term Store.
The Term Store Admin Center includes an Excel template that shows how a file must be formatted to import. To download the template:
- Go to the top level of your Term Store
- Select “View a sample import file”