this is of course all part of the still unwritten manual pages
so...1. the user
preset saving is in the works... the plugin already shows up all the options - they are just grayed out. right click any material this would be "save as user preset" (will show up and work much like the live db, just locally saved), render settings and environment settings have this option in the copy dialog. this should arrive within april. current doggy workaround would be to save a bunch of settings into an empty scene to merge it into another.
2. this is intended behavior - in fact these initial settings are no "presets" just some default settings. they are edited like materials and will keep their settings whenever changed - but you can have as much of them as you like. just use new/copy right beneath the dropdown box to create new render- or environment settings, you can switch them end edit them individually of course. so there is just no need to save something, but currently they are only kept within a saved scene (refer to pt 1.
)
this leads me to
3. whenever you create a new render setting, or a new environment setting, you will get the same default values like the initial default settings had. thus there is not necessarily a need to restore defaults, since you can of course switch settings whenever you want - name them to your likes (with "rename" of course
) or delete what is no longer needed... should be all you need.
in other words: the plugin starts as if you had clicked "new" for render settings once, and "new" for environment settings twice, creating one daylight and one hdri environment. only the no/null environment is a fixed option, that can not be altered (or copied) since it is naturally only needed once in one flavor for all time: darkness
a note about the kernel switch: each render setting will of course allow to switch between all different kernels. additionally each kernel will also keep it's settings, since you usually want to quickly change i.e. direct lighting and pmc kernels without loosing the current values. and again: copying the whole setup should allow to create as much combinations for imager/kernel/... settings as needed.
i hope this all makes sense... if not - then there was some misunderstanding on my side... or there is a bug