How to undo Update Changes?
Using Jamroom
It sounds like you are making modifications to the modules/jrCore/templates/editor.tpl directly - you do NOT want to do that - if you modify that file directly, it will be overwritten every time you update to a new version of the core.
Instead, you need to make a COPY of that file in your active (cloned) skin directory - i.e.
skins/YourCustomSkin/jrCore_editor.tpl
Makes your modifications to THAT file and it will be used in place of the one that comes with the Core.
You can also make your modifications from the ACP -> Core -> Templates section - any changes made there are NOT overwritten when a new core module comes out.
See the "Never customize templates in the module or skin directories!" section of this guide:
https://www.jamroom.net/the-jamroom-network/documentation/problems/1527/i-just-upgraded-and-lost-my-changes