How to find what ctrl+alt+up/down is mapped to?
All native macOS shortcuts are mapped through Settings > Keyboard > Shortcuts

You can search through all the lists and look for the following combination in the right hand column: ⌃⌥↑. When you find it, you can either disable the checkbox in the far left or change the shortcut by double clicking it and entering a new shortcut. 

You should now be able to use that shortcut in any program that the developer has mapped that for.