An old coffee incident has left my laptop’s left Ctrl key broken so I have to use the right Ctrl key instead. Unfortunately Renoise seems to explictly require the left Ctrl key for shortcuts and the right one does something else.
Having to use the menus for every operation is getting real old - any way to swap the left and right Ctrl around? 
I assume you are using version 1.5.2.
In the Configs=>Keyboard/Mouse menu, you can edit your shortcuts.
The new 1.8.0 version (currently available in beta for registered users, but really close to public release) allows for configuration of almost any keyboard shortcut (apart from RCTRL,RSHIFT and some others), while 1.5.2 is a bit more limited in this.
No, I’m using the 1.8 beta. Unfortunately there are too many shortcuts that need lctrl and I can’t remap all of them. I was hoping for a “swap ctrl buttons” option but it was asking a bit much 
I’ll just keep using the mouse menus while on this laptop.
Using some advanced text editor like PSPad, you could open the KeyBindings.xml in the Renoise application data folder and do a search and replace for the keys. Don’t forget to make a backup.