Is it possible to set a debug point in FreeMarker template file?

As far as I know, you cannot. A template file is a plain text file that the template engine reads into memory and then uses to produce a document that it writes to the response. It's not actually executable code. You can put a breakpoint in the template engine code and follow along what it replaces and how.

FreeMarker has a debugging API, although it has stuck in experimental state eons ago, mostly because nobody has taken the effort to write a front-end for it (like an Eclipse plugin). Except, I know they have planned to support it under some of the next LifeRay IDE versions. As far as I know they managed with break points, but there's no support for stepping in the FreeMarker API for example.