I defined a function description.ext:

CfgFunctions
{
class MyTag
{
class Mycategory
{
class myfunc {};
};
};
};

and added function file fn_myfunc.sqf to [missions_folder]\functions\Mycategory

Then I started the mission and used debug console to recompile function after making some change:
"mytag_fnc_myfunc" call bis_fnc_recompile => didn't work
1 call bis_fnc_recompile => worked