Why am I unable to view the sub-categories while creating expenses?

If you want to view the sub-categories while creating expenses, you should have enabled the parent categories. To enable a category:

To create a new category:

1. Switch to Admin View.
2. Click the icon in the top right corner of the page.
3. Go to Customization and click Modules.
4. Click Categories.
5. Apply the Inactive Categories filter and select the sub-categories you want to mark as active..
6. Mark the Make this a sub-category option, if it’s a sub-category.
7. Click Click Enable.