How hard is it to mod a Jazzmaster 3 way pickup selector switch to go from left to right

[Wavedash]

instead of top to down? Sometimes when sitting, my leg will slightly touch the switch and there will be some static (in the middle position only though).

[solfege]

instead of top to down? Sometimes when sitting, my leg will slightly touch the switch and there will be some static (in the middle position only though).

Vintage / factory settings are typically left to right -- though when I first got my '90s MIJ (new), it was at about a 45 degree angle, so who knows how consistent that's been? But it should be as simple as loosening the nut holding the switch in place a little and turning it until it's at your desired angle, then retightening while holding in place. If that doesn't work (and it might be hard to get it to stay where you want it while retightening), taking the pickguard off and holding the back side in place while re-securing the nut should do it.

[Bradley-Jazz]

On my MIJ, when I installed a new switchcraft, it shorted out on the shielding I'd put on the cavity if it was left-to right, so it went back to 45 degrees. Your routing (or shielding) might be different of course.

[Embenny]

Exactly, different JMs have differently-shaped switches. All you gotta do is loosen the nut and rotate, provided there is enough slack in the wires to do so. I've wired a lot of offsets and haven't personally had any switches short out due to finicky positioning. I like to angle the switch to fit naturally with the directional my strum.