I have an x5d, but I think the x5 is about the same for effects.
In a multi setup you only have the choice of two effects at once. To be able to set an effect for one track you have to set the placement (multi page 20) to parallel 2. This will separate the two effects - one going to Pan A&B, the other going to Send C&D. Then assign the effect you want for the one track to either the Pan or Send. Set the other tracks for the other (Pan Or Send)that you don't pick for the initial track. Say you want to set the rotary effect for an organ patch by itself, but you don't want the other tracks to have rotary. In the program mode set the rotary effect to be effect #2 on the organ patch. Go into multi mode and go to the organ track, then go to page #7 and set the Pan to OFF. Go to page #08 and set the SEN to 9:9 (max). Then go to the other tracks and assign Pan to CNT (center) and SEN to 0:0. Then those patches will respond to whatever effect you set in multi mode as effect #1. Other than those two effects, you can't make a different effect for each patch. (I wish you could) Hope this helps.
mutt