Most VHDL files in any organization start with the same few lines: a copyright header and the same few library and use clauses. It's a pain if you have to go look for another file and copy and paste the header.

Instead, it is a lot easier if you just define a template for your copyright header and for your default library and use clauses. You can then insert these templates by typing "copyright" or "libraries" then and pressing CTRL+space.

You can create your own templates by going to the preferences Window > Preferences and then Sigasi (VHDL) > Templates. Click New... and fill in the template dialog. You can also insert variables such as ${year} or ${user}, which expand to the current year and the user name, respectively.

see it in action