There is no application exactly.
Look into Boiler - Insert a selection of documents by Graham Mayor, MVP.
Look into AutoText: Automated Boilerplate Using Microsoft Word

You can use conditional text with an IF Field that will test for a condition you set.

If you go the vba route you may still use some of these techniques to hold the parts to be inserted. I would recommend a UserForm.
Create a Simple Userform by Graham Mayor, MVP

Create & Employ a Userform by Greg Maxey, MVP