Here a patch to add context to small strings which are very hard to translate (i.e. "p", "s", "fb"). There is still a "p" without context in the mainpanel.glade file, but it looks like there is no way to add a translation context with glade language.
It also remove translatable feature for some strings, like arrows ">" "v".
It also avoid to generate a translatable N_("?") string from faust .dsp (gx_ampout_ladspa.dsp, and gx_outputlevel_ladspa.dsp). It looks like that groups ("declare groups") without a label (i.e. group[label]) generate N_("?"). Then i add a default label (i.e. .amp[Default]). It may also mean that this groups are useless and we can remove them, but i dont know that language.