Step 1: Build a sheet by dragging the dimension and measures.
Step 2: Use 'Ctrl+shift' to select the sub-categories you want to group. After you group these three sub-categories together, you should see the name of 'Sub-category' change to 'Sub-category(group)' on the top of the sheet.
Step 3: Click the upside-down triangle on the right of 'Sub-Categor(group)' and choose 'Edit Group...' from the drop-down menu.
Step 4: Click 'Rename' on the pop-up window. After you see the blue color of the group change to white color, you can start typing directly on 'copiers, machines, supplies'. The next text will automatically rewrite the old text.
Step 5: I renamed the group to 'Sub-Categories(<200)'. The order of the sorting changed.