Most fields have an existing item list so while adding or updating an entry:

1. Tap the desired field.
   
   
2. This brings up the method to enter the information manually but now below that is the existing items list with a search field.
   
   
3. The search field that can be used to filter a longer list.
   
   
4. Tap here to learn how to remove items from the existing items list and add them to the exclusion list.
5. When you find the value you want to reuse, simply tap it and that value will be added to that field and you will be taken back to the edit screen