Try exiting SlickEdit, deleting your vrestore.xml and vrestore.slk (if you have one). Also delete all your *.vpwhist and *.vpwhistxml files. This will clean out all the docking state information.
SlickEdit Pro 2024 (v29.0.1.0 64-bit Qt5) hotfix 4
I am finding that these tool windows keep docking each time I start a new instance of SE: - Find Symbol - Interactive - Clipboard - Highlight - Bookmarks - Terminal
I unmarked Dockable for each of them, but each time I start a new instance of SE they dock when invoked.