DSSI wouldn't be a solution here, guitarix support already per effect pre-sets, as well as external UI's for LADSPA or internal plug-ins. We handle plug-ins (for now LADSPA, external guitarix plugs or internal plug-ins) over our own plug-in API, witch makes this possible. LADSPA plugins get wrapped to it, and the missing features get added.
Also, our LADSPA load widget gives advanced users the possibility to have a high influence on the UI for the selected LADSPA plugin, additional users can create a UI for any plug-in with glade if they wish. Otherwise guitarix create it automatic.
Anyhow, the problem with jack-rack pre-sets is on a other sheet, guitarix simply only support mono or stereo plugs, means only plug-ins with equal in and out-put ports not more then 2. are supported.
Guitarix itself could be simplified seen as 2 racks, a mono rack, followed by a stereo rack. So, mono plug-ins could only loaded into the mono rack, stereo ones into the stereo rack. Now, even if we could wrap jack-rack pre-sets to the guitarix pre-set format, loading will fail in most cases, because we can only load mono plugs before stereo ones, and cant load other plugs with non-equal or more then stereo audio ports.
To the NSM support, sorry Rosea, it's like I said in the other thread, I have nothing against add support for it, only my interest in it is low, so a patch will be welcome, as well as project members to implement it.
We have add LADISH support in a early state of the LADISH development, now we are marked as broken, because LADISH cant handle multi client apps. We have add jack-session support as well in a early state of the session API, now, it seems that development of jack-session is dead, and NSM comes in the game. Well, before I invest time in it, I will see if it becomes stable, otherwise, I have a bunch of other stuff on the to do list for guitarix already.