I`m swapping the levers on my Shimano XT M765 hydrualic brakes.(From DCL to conventional levers and rf shifters.)
Can I simply,undo the hoses,stick a new olive on the end of the hose,screw on the new levers,top up the reservoirs and be done with it or will I need to bleed the whole system?
Would it be better to add new fluid with a syringe at the caliper end,once the new levers are fitted?

I think I’ve done it without bleeding – juts make sure no air can get in to the join.

Take the pads out of the callipers and pump the brakes out before you start. Swap the levers over, reconnect then lever the pistons back in to the calliper. Top up with fluid and you are done.

I managed it. Keep the open end higher and any bubbles will stay there. Reconnect and pump. You might need to top up the reservoir a little bit (assuming yours are the same as my old ones internally).

When I took the hose out of the lever (squeeze lever a bit to budge it), no fluid escaped, so didn’t need to bleed. Just top up the reservoir, should be fine.