Riosmma

Perhaps i'm unaware of this feature, but it would be really nice to see an option to undo a change. I've deleted entire paragraphs, charts etc by accident on multiple occassions and its enough for me to want to light my computer on fire. Seriously, its such a basic funtionality that I must have missed how to do it otherwise it seems very silly that this isn't an option. Can someone help me if I am missing it? Thanks