You can prevent the default popoup menu by adding an empty (no menu items) TPopupMenu to the form and assigning it to the TEdit.PopupMenu.
Internally TStyledEdit checks (in TStyledEdit.ShowContextMenu() ) if the PopupMenu property is not nil, and if so, shows the user defined popup menu, otherwise it shows the default popup menu
https://docwiki.embarcadero.com/Libraries/Sydney/en/FMX.Controls.TControl.ShowContextMenu ------ try set to NIL popup from component, try use "hack" to access it if not possible directly....
type xxx = class( zzzzz )
... xxx( cccc ).PropertyXXXX = ???
--- you can try send PostMessage() when popup is opening... PostMessage(ComboBox.Handle, CB_XXXXXXXXXX, Cardinal(-1), 0);
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The higher the degree, the greater the respect given to the humblest!RAD 11.3