That means every mousewheel moving:
1) get fx under mouse cursor,
2) get mouse pointer position relative to this fx gui in mcp,
3) move fx up/down in chain,
4) set mouse pointer position to this fx to xy value previously stored.
Yes, I can just move fx by left drag, but mousewheel is easier for me. After every moving I see the result. When I just drag fx, I should care about where to release mouse button. This a bit frustrating, especially with high resolution screen / little theme elements.