Is there any way to modify this blue boundary? It appears to be some kind of label but I am not sure how to create or modify this label. Thanks.

Have you tried unlocking the hidden layers?

This is a port label, looks like in a standard cell. You seem to have all layers hidden? Or how did you get to this view? If the label/port is in the top level layout being edited, then you just need to have the cursor box around the entire label area, including its label area box, and then you can use

erase labels

to get rid of it. But if it's in a subcell, especially a standard cell, you don't want to be messing with it.