Open Source Document Management System | OpenKM

What is the problem with CTRL+Z ?

I suggest using the methods disableKeyShorcuts() and enableKeyShorcuts(), a good class to watch the implementation might be KeywordsPopup.java, if you understood how is used there you should success in use in rename.

https://github.com/openkm/document-mana ... Popup.java

Are you sure about the disable shortcuts method has really executed ( put some Window.alert )?
Did you make a fork of OpenKM source code? that is a good practice to compare and build your changes from our side.

In the extendedDocPanel comment the line
dockPanel.sinkEvents(Event.KEYEVENTS); // all the shortcuts should be disabled and then check the code. If that works I suggest uncomment and check the disableKeyShortcuts and ensure the enableKeyShorcuts is not called from other after you have called disableKeyShorcuts

disableKeyShorcuts() should make the same, at least you will check if the problems come from there, seems in your case is not working ?

In the professional version, we have the option to change CTRL+Z to another shortcut from profiles. I think that feature was introduced for an issue with a German keyboard. Unfortunately, these changes have still not promoted into the community edition.
An option might change CTRL+Z in your the code for a shortcut like CTRL+SHIFT+Z, or make this keyword configurable in a similar manner we have done in the professional edition.