First of all, check that it is still assigned (in Tools > Editor > Keymap). Maybe something else got put in place...
Second: Your OS, and Lazarus version?
Third: I have see occasional issues with keys not working as expected under anchordocking. but I am uncertain what exactly the issue is (iirc there are some issues on the bug tracker).
- Try to assign to another key combo
- Check if it is certain other Windows (or controls/edit/input...) that block this from working.
It could also be, that the key is working, but focus isn't correctly set.... (would the key combo open the search dlg, if that was assigned?)
When you say AnchorDocking: That is just Anchordocking[Dsgn]? (maybe including DockedFormEditor).
But it does not include anything with "Sparta" in the name? Those "Sparta" package are broken. Don't use them.