There are a few ways to accomplish this:
1. It can be moved with the "Free Move" tool (or Free Rotate). These are on the Position panel. As the names say, these will not allow you to reposition a part/sub-assembly, as it is a temporary action, and the moved/rotated items will eventually snap back to their pre-operation locations, provided they were completely constrained or grounded.
2. If the part/sub-assembly is not "Grounded", modify the "Offset" value in the constraint dialog that locates the item in the direction you want to move. This option may not give you the result you want, if other items are constrained to the item you want to move.
3. If the item is "Grounded", then un-Ground it and move it where you want. This option also, may not give you the result you want, if other items are constrained to the item you want to move.
4. If you don't need to see it, "Suppress" it, or change its "Visibility"
The last 3 options can be tied into LOD's, View Reps and Pos Reps if needed.