This is perhaps equally dangerous as doing string replace
1. Scrape over the variable name in question to highlight it.
2. Hit <ctrl>C
3. Hit <ctrl>F
4. If this method is going to work the FindAndReplace menu should have the variable name in the Find: box.
5. Type the replacement name in the Replace With box.
6. Click Replace All.
7. Click the Yes you really mean it.
Use that carefully, perhaps by making appropriate backups so you can more easily recover from disasters.
I believe I have at times in the past had this refuse to correctly deal with some special characters or strings
and had just given up assuming that those were not possible, but I cannot come up with an example at the moment.