It is possible to compile a modulate new of synfig to generate an effect? As I can do this?
synfig/synfig-core/src/modules/mod_example
gcc ... (?)I wish to generate an effect of image…
There is wiki.synfig.org/Developer_Documentation
But it depends on what you want to implement (mod, layer…)
You have to include the proper .h (depending the task) and modify .am/in files.
Of course you will have to modify the GUI as well to instanciate the module in app.cpp and give some access (through menus for example).
Not so much easy in fact 
Go back to compile all, is very bad :’(