Try adding a coordinate system in reference geometry.
I think what you want to do is change the sketch origin orientation. If that is the case it is ridiculously difficult to do but you can do it with the modify sketch tool. First you have to figure how much you want to rotate it perhaps by making a sketch horizontal to the the WCS. Close that sketch then start a new sketch on the surface without any relations whatsoever. Use the Modify Sketch tool and rotate the sketch origin direction to what you need. You can do other things from this dialog like mirror by clicking on the black triad but that is not what you need.
but you may need to flip the x or y axis by right licking on a corresponding black dot.
Note the sketch x axis direction now.
I rarely have done this and every time I do I spend about a half hour trying to figure it out again. There may be an easier way but I haven't figured that out and can't remember if I have seen one. Unless you have a great need to orient your sketch differently than the WCS I would just use conventional stuff like horizontal relations, angle dims and what ever.
I think what you might want is the Align tool. Look in "Tools, Sketch Tools, Align, Align Grid/Origin". It's way down toward the bottom of the Sketch Tools menu.
In this quick example I started a sketch on an angled (relative to the default planes) surface and reoriented it so that the origin is at the lower left vertex (red triad) and Y is aligned with the long edge (not the one highlighted in the screenshot). Note the blue part origin triad, to the rear, is no longer aligned with the sketch origin.
That"s it Erik... I knew I had forgotten something.