Flexible Toolbar customization: be able to add any custom command, or any existing action (examples: fetch, clone ...)

Toolbar customization is quite limited in the choices of actions in offers.

For example, you can't add a Toolbar button for Fetch, nor you can add Clone or many other actions.

Another important missing piece is custom Actions (Commands), if you ever define your own, then you probably like us would definitely want it on the Toolbar, which currently you can't.

Thanks