I've created a plugin collective.ptg.unitegallery for plonetruegallery that implements the very good Unite Gallery library. The module is distributed as 1.0a2 version on pypi and on github collective.
There are 8 different displays with a lot of different options. I haven't had enough time to add all of them, so help is welcome.
There are so many options that the form becomes very long and difficult to understand, unfortunately I haven't found a way to have group of fields in the form nor hide fields depending on other fields.
The plugin shoud be compatible with Plone 5 (tested) and Plone 4 (not tested).
I will try to help a little (but I am extremely busy at the moment, so would it be possible to update the readme with 'to do' or something similar so I know what should be done 'first'
I will also add the unitegallery options but I'm also quite busy now.
However everything is working fine so far (on Plone 5) even if it's not possible to define each gallery details for each theme.
The Interface definitions are not very smart as there are often same options shared between themes and so I've duplicated the fields (no way to merge interfaces together).
Is making each 'gallery' its own package, which all requires the 'core' package that keeps all the base settings which are then shown in its own frameset ( I dont think we can make a frameset inside another frameset)
Actually, I think it should be possible to 'merge' the interfaces, I think it is done here: