I suggest continuing to use the existing simple syntax convention for relationships to add any grammar. This feels more in line with the outliner DNA of Logseq, as it uses the block hierarchies to encode information, and keeps everything visible in the markdown (rather than in an extra layer of data that only exists within the plugin).
Use the existing syntax and create a new relationship (calling them whatever they want, here I use type
)
Then to actually restrict relationships, the plugin could reserve a special relationship (e.g. grammar
) for declaring the grammar of a relationship: