@Override
		public boolean isDropOk(DropTargetDragEvent e) {

			Component targetComp = e.getDropTargetContext().getComponent();
			if (!(targetComp instanceof JLabel)) {
				return false;
			}

			updateActiveIndex(getLabelIndex((JLabel) targetComp), -1);

			try {
				Object data = e.getTransferable()
						.getTransferData(SelectionTransferable.localProgramSelectionFlavor);
				AddressSetView view = ((SelectionTransferData) data).getAddressSet();
				if (memory.contains(view)) {
					return true;
				}
			}
			catch (UnsupportedFlavorException e1) {
				// return false
			}
			catch (IOException e1) {
				// return false
			}
			return false;
		}
Set the mnemonic text and attributes
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/references/InstructionPanel.java