Can we extend the built-in Ribbon options using Office js manifests?

Question

I'm writing an OfficeJs addin for Excel that provides an additional Copy action for cells. Ideally, I'd like to add a custom menu for it on the Home > Clipboard > Copy dropdown, below "Copy" and "Copy as picture". It seems wrong for me to take up a whole Ribbon group, just for a single menu item...

I was hoping to add a menu item to the Copy menu with:

                    <ExtensionPoint xsi:type="PrimaryCommandSurface">
                        <OfficeTab id="TabHome">
                            <Group id="GroupClipboard">
                                <Control xsi:type="Menu" id="Copy">
                                    <Item id="myId">
                                        <Label resid="myLabel" />
                                        <Supertip>
                                            <Title resid="myTitle" />
                                            <Description resid="myTooltip" />
                                        </Supertip>
                                        <Action xsi:type="ExecuteFunction">
                                            <FunctionName>MyFunction</FunctionName>
                                        </Action>
                                    </Item>
                                </Control>
                            </Group>
                        </OfficeTab>
                    </ExtensionPoint>