The terms of the trust should indicate under what conditions and how any modification of the trust is to be made. Your ability to change the trust may also depend on who you are - the settlor who may have created the trust or the trustee who is responsible for administering the trust. In some cases, you may have to get a Court order before any modification can be made.
Your best bet is to consult with your attorney and have the trust reviewed.
Most trusts will state if they can be changed and how you make that change. Generally, writing directly on a trust will not be valid, and in fact, may actually invalidate the entire instrument.
If the trust is a Revocable Trust or a Living Trust and you have reserved the right to change its terms, you would need to write an Amendment to that Trust that would be executed using the same formalities as executing a Last Will & Testament.
You will be well-served to consult an attorney to make certain that your wishes are properly and legally documented.
You are not able to change a Trust in Florida by crossing items out. A simple amendment would accomplish your goal. Crossing a name out could lead to litigation in the future because it creates an ambiguity in the document. The law regarding execution of your documents has been put in place to protect the integrity of the documents, so that another person can not just come after the fact and change your Will or Trust. You should be able to the same Trust that you have with just an Amendment to the Trust to reflect the change.