The Redo button is available on the collection toolbar for all tabs. Click the button on press Ctrl+R on the keyboard to redo the last undone change.
The redo history is separate for each tab, just like the undo history. You can only redo changes immediately after undoing them. If you undo multiple successive changes, you can redo all of them. But as soon as you make another change that's undoable, the redo history will be cleared. The only exception are trivial changes like moving the text cursor or selecting another clip. Those won't clear the redo history. If you redo an undone change after making a trivial change, the trivial change is undone before the action you wanted to redo is redone.