You’d be better off looking elsewhere for a solution:
Given other needs, this one would likely get a low priority (we’ve run Clarity/Niku/ABT for years without anyone accidentally deleting a project – yes, can happen and your idea is a better solution, but this wouldn’t make our priority list)
We are looking at, and gaining support for the purchase of LetzNav<https://letznav.com/>. Take a look at it. LetzNav will allow you to create and display your “Don’t click…..” message, and solve many other user notification, training, help issues. Works with Classic and New UX. Also, can be used with many other apps (contact LetzNav regarding their licensing model). This should be in our budget for next year – can’t wait.
Dale