I've recently tried to toggle a widget from beeing dragable to not beeing dragable.

What I did setting the corresponding Flags for ignoreMouse and draggable to 1 / 0 by doing

int flags = widget.GetFlags();
flags = flags | 32768 // not 100% sure which but it was for each of them
widget.SetFlags(flags);
widget.Update();

No matter what I tried, the Widget was still not dragable.
I did a small workaround by just deleting the old Widget by script and creating a new one, which has the same .layout file, but with ignoreMouse and dragable set to the opposite values, which is not really optimal. I used flags when setting the positioning of the widgets, which seemed to work just fine, but for some reason, it does not work with ignoreMouse and Dragable (maybe some kind of registration which only happens if the widget was dragable from the beginning)