When Ctrl-z doesn't work, does TB Menu Bar > Edit > Undo work?
How soon after deleting are you trying it? It works for me even after reading more messages.
(Most don't see the top [menu bar](https://i.imgur.com/OTvCzJ6.png), as it's hidden by default. If you don't see it, press the ALT key. To make the menu bar always visible, press ALT + V, then T, then M.)