Yoshimi works great as an LV2 plugin but the internal sound banks do not appear to be exposed as LV2 presets, the following returns an empty list:
$ lv2info http://yoshimi.sourceforge.net/lv2_plugin
It would be great if the presets were accessable via LV2.
Unfortunately the person who did all the LV2 work it quite overworked lately, and I'm deeply involved in other parts of Yoshimi. However, I'll put it on the 'todo' list.
I think this may be complicated by the fact that there isn't a fixed list, but completely user-definable groupings.
Meanwhile, you can of course access them if you bring up Yoshimi's native GUI, and can also reach them via standard MIDI bank & program changes.
It appears that some of the presets appear in Carla (never used this before). I'll see if I can find out more.
This hasn't been forgotten. Unfortunately we still don't have anyone on the team able to improve our LV2 implementation.
I think one challenge with presets is also that if they are available, they risk overriding other changes that you make to the patch. So they can be quite destructive. If you just quickly select one, perhaps by mistake, you've ruined everything else you did.