The invention relates to a rotatable indexing unit for a manual control member (2), comprising two indexing components (31, 32) one of which is the rotor (32) rotatably secured to said control member and the other is the stator (31) which is embodied in such a way that it is fixedly maintained with respect to the rotor. The rotor and the stator are mounted coaxially and comprise a plurality of angular segments (317, 318, 327, 328) at least some of which are magnetised in such a way that they define stable and unstable positions for said control member, and the rotor and the stator have a conical or tapering shape which makes it possible to reduce the required radial space and increase the so-called active surfaces of interaction between the magnets.