All those buttons can be create and customised by you, as your new to samba i suggest using the search function as theres a lot of information and tutorials to help you learn and customise samba
Hold Button - do a search for hold orders or layaway or suspended sales. I have done a tutorial for this ill find and attach it
This tutorial can easily be adapted and change he wording from bar tab to held orders or similar
Cancel Order - theres already a button to remove an order from a ticket. If you want to creae a button to completely cancel the ticket/transaction this again is documented with a tutorial on how to create it, search for abort order
Send Order - this is pretty much what the close button does, the close button submits the ticket and the orders. You can add some actions to this rule to add functionality to send orders onto a kitchen screen when the close button is pressed. You can also rename this button to say send instead. There are tutorials to help you setup a kitchen display, this will be the more complex of the things to achieve
That should get you started and some have a database tooks file so you can directly import the setup into yours, always backup before you import anything