You can add other word lists to a word list and remove the words in one list from another list using the Word List Manager.
Adding other word lists
First select the list that you want to add the other lists to, then select Add other lists... from the Word List menu. Select the word lists that you want to add and change the score settings as desired. When you press the OK button the lists will be added, and you'll be shown a summary of the changes that have been made.
You can also right-click on a word list and select All list to other lists to merge that list's words into one or more other word lists.
Removing words from another list
Select the list that you want to remove words from. Then select Remove words from... from the Word List menu and select the list(s) whose words you want to remove. When you press OK the words will be removed, and you'll be shown a summary of the changes made.
If you want to modify a list but keep a copy of the original you can use the Duplicate list command on the Word List menu, which creates a copy of a word list with a name you specify.
You can also right-click on a word list and select Remove list from other lists to remove that list's words from one or more other word lists.
Select the equivalent words option if you want the action to be applied irrespective of case or punctuation (according to the list's letter mapping and punctuation setting).