Keyboard shortcut - customize rotation

[mustbeit]

MP 0.96.4
It's possible to customize keyboard shortcuts under:
Tools>Parameters>Interface>Shortcuts

However, I do not see the possibility to create a shortcut for custom rotation, as it is possible for 90degres rotations.
I missed something or it must be posted under the "suggestion" forum

Thanks

[xnview]

what do you means by 'custom rotation'?