We can review, comment, merge, reject, retract Pull Requests in SmartGit, but we can't approve them yet.
I'd suggest a simple branch context menu entry and a Review menu entry for this: "Approve Pull Request". Ideally, if this user already approved the PR, this should change to "Unapprove Pull Request".
Another helpful improvement:
Add two buttons or options to the "Add Comment" dialog, to set Approve or Needs work, analog to Bitbucket Server.
The buttons would have the same function as "Add Comment" button plus additionally set the Approve or Needs work flag.
The options can be toggled and would fire when "Add Comment" is pressed.
As a Needs work status should be explained, I'd limit this possibility to the comment dialog.
Customer support service by UserEcho