You're able to track your work after the Done column, by adding additional columns in the "Closed" section. These columns track work after an issue or pull request is closed, for example a "deployed" column or "accepted" column.
You can configure how your columns are set up in the Columns section under Project Settings.
How it works:
Take this board for example: the Done column does not have a column label but the QA and Production columns do.
Because the Done column doesn't have a column label, all merged PRs will go here first. You can then manually move cards to other columns after Done.