To reference any of en Entry object's properties, just use <Entry object>.<property name>, like entry().name.
So, I opened an existing library of mine that already had an Update/Before trigger, and added one line.
The line was:
message("Last modified " + entry().lastModifiedTime);
After I edited and modified the first entry, I pressed the checkmark icon and saw the following at the bottom of the screen for two seconds:
Last modified Fri Apr 07 21:11:15 EDT 2017
It sounds like you would need to do what you're doing in a Creating / Before opening and an Updating / Before opening trigger script, especially the latter. It should work there. You'd see it in an Entry View card, but not updated yet in a list entry.