Thanks so much for sharing your feedback! While there is an “undo” button that pops up for 30 seconds after, having a warning before deleting it would be super beneficial!
We’d love for you to add this feedback to our feature requests here! Our product team takes a look at the features with the most upvotes and many end up on the product roadmap!
While it is not on every board, when you have items connected in the board, this pop up does appear: