There are some ways to reuse taxonomy or instance files.
A. Copy taxonomy/instance files and edit the copied files.
This may not be a solution, but it is a simplest way to reuse taxonomies.
B. Use the taxonomy comparison function.
1. Open a new taxonomy using Taxonomy Editor.
2. Select the menu "Tool > Compare Taxonomies ..."
3. Open the old taxonomy. (Select "No" if an confirmation dialog is displayed.)
4. Select differences and click the "Override & Update" button to copy the
required information from the old taxonomy to the new taxonomy.