Hi, just signed in newly –
after having had Mochi Cards in the focus actually for quite a while indeed, because I intended to take notes “block-wise” and remember the content with the help of Spaced Repetition and Cloze Deletions (covering parts of the text in review mode and letting you looh at it only after tapping it).
The structure of Mochi is quite similar to SN, only lacking a bit of the features fdr note taking.
First I intended to make notes as blocks either in Logseq or Dynalist (to have a structured learning document) and then copying them over into Mochi.
I’m beginning to think now that maybe SN might be a better option to create the cards all ready (including marked with cloze deletion like this {{covered part of text}} already and in some way export them in bulk to mochi.
Creating .mochi files shouldn’t be that difficult, it just needs the decks name (i. e. title of the parent card) and the notes’ contents, brought into a specified EDN format that is zipped after (Mochi site specifies that exactly).
As SN is lacking Spaced Repetition itself it might be beneficial to offer users the chance to do SR via Mochi (own .mochi files can be used free of charge) as they wish. In case this was in your range of interest I’d suggest to just add .mochi to the possible export formats.
Another way to add specific cards would be to use Mochi’s API - best by adding a special reserved tag like e.g. @rep-deckname or something like this, that triggers the use of the API upon refresh. Exporting .mochi might be already enough I suppose - and surely much simpler to implement.
Personally I can see a lot of use in that, also in respect of surfacing cards (when they appear regularly in Mochi you simply DO surface them all automatically if you wish to do so - the use of cloze deletions is always optional)
SN is so far reaally great, just to mention! 
Thanks for all the work the team is putting in here