Is there any such thing as an undo button with Glide?
I copied a template with a lot of scripts and am just editing a few aspects of it for a client. And if I accidentally click back on the page or switch to a different view and then back to the original all the scripts and everything is gone and there’s no undo buttons, save buttons, etc. I’ve recreated the app 5 times and if I make any small mistake I have to restart all over yet again.
Did you actually copy the template to your apps first? If you edit templates before copying them, your changes are never saved and you’ll experience what you’re describing.
Yes, I always copy it over first and save it. Say I accidentally delete a line of code or something from a box, markdown text, etc. How would I go back and undo that and get it to reappear?
There is no undo button at this time. What exactly do you mean by “scripts”? Do you mean changes to components?
Yes, components, visibility, conditions etc.
For example the Instagram app, If I look to see the different layouts for the “Your profile” tab for lets say compact list or the checklist styles and then come back to the default details style all of the rich texts, conditions, and whole buttons themselves completely disappear where those features were attached to the back.
Yes, you have to be really careful when changing the style layout. Many people have ran into the same issue. Once you do it you never forget. 
I’m hoping that in the future, Glide will eventually save the layout for each style, or at the very least, give a warning that the layout will be lost.
Looks like they are releasing an update tomorrow: