Updating action buttons in top tool bar - add/remove, update permissions

[Amy_Gregoire]

I have been tasked with making some updates to the buttons in the top tool bar on REQ records, but I am not sure where to find the ability to make these edits. Could someone point me in the right direction? 

Specifically, I'm looking for info on the Cancel Request button. thank you

[Slava Savitsky]

These buttons are UI actions. Navigate to System Definition > UI Actions and search by Name = Cancel Request.