Does any one have any experience with cutting a carbon steerer whilst leaving hydraulic cables in situ?
I think it would be possible to get a guide around the steerer, and maybe use a dremel to cut small sections and move cable out of the way?
You will want the abbey bike tools saw guide. This is the best tool for what you are describing. Because it fully opens up for cables to pass through and then you can clamp it down and cut straight. I am not sure how well the park tool guide would work in your situation but may be ok
totally doable as youre describing but I think youre gonna spend more time prepping than it would take to just pull the fork and reassemble. you accidently nick a cable with your dremel and your work time just tripled re-running a brake hose. Will you have enough space to clamp your guide with the headtube in the way, are you littering your bearings with carbon shavings? Im intrigued though, let us know if it works!
there is always some room for slack, hoses get tucked into the frame of the bike/fork and can curve a bit to account for the extra length. Otherwise it would be impossible to turn or take the handlebars off.
Cutting the steerer by a ~normal amount (perhaps 1-2cm) doesnt create enough “excess” hose to make a problem.