private void splitBlock() {
		MemoryBlock block = getSelectedBlock();
		if (block == null) {
			return;
		}
		if (block.isOverlay() && block.getStart().isNonLoadedMemoryAddress()) {
			// impose convention-based restriction
			Msg.showInfo(getClass(), getComponent(), "Split OTHER Overlay Block Not Allowed",
				"OTHER overlay blocks can not be split.");
		}
		else {
			SplitBlockDialog d = new SplitBlockDialog(plugin, block, program);
			tool.showDialog(d, this);
		}
	}
Pop up a dialog to split the selected block.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/memory/MemoryMapProvider.java