Articulations for fixed pitch notes

I don't seem able to set articulations for fixed pitch notes (brown symbols).  That section of the figure parameter (called "segment" is greyed out).  If I change the symbol type the section with articulation becomes available. 

I have tried a work-around: Change symbol type to any other type. Add articulation.  Put the symbol type back to fixed pitch.  That works to some extent but the results are inconsistent, especially with the first note played.  It is a bit of a nuisance anyway.

I like to use synfire to write accompaniments to fixed pitch melodies so it would be handy to be able to change articulations for fixed pitch notes.

Would that be difficult to implement?

Thanks.