Gtmhub allows you to send reminders to people who you are selected as reviewers in the approval workflow, but have not yet approved your OKRs.
To send reminders, perform the following:
In the navigation pane, under OKRs, click All session.
Click the session where there are still OKRs for approval.
In the toolbar, click the Approval progress tab.
In the Reviewers with pending OKRs section, click View list.
Click Nudge people.
Enter your comment and click Post.
This comment is posted on each OKR that is pending for approval with mention of each of the reviewers who have not approved yet.