@anon-3t
On Mac, reinstalling also fixed it. I also backed up my word database to be safe, but it did pull it in from Migaku cloud when I clicked sync in the settings menu.

@anon-12f
I also found this post:
https://www.reddit.com/r/ImmerseWithMigaku/comments/w9wvba/issue_selecting_target_word/

so you could quickly hover over each unknown red word, press '2' to mark it "seen", until you just have one unknown word left then press 'q' to make a card for it. Then you toggle the first word back to "seen" with '1', mark the next word "unknown" with '2', make a card with 'q', rinse and repeat. Still kinda sucks but I think it will be faster than creating cards from the dictionary, or duplicating and modifying them on the Anki side.

@anon-10i
+1
Switching from Language Reactor to Migaku and having the same issue.

I love sentence cards, but while i'm building up a base vocab I want 1 word per card so I know how to grade it.

My current workaround is to hold shift over one word to bring up the dictionary and create the card that way, but it's a bit more manual to add the sound clip and google image, etc. I also don't see an easy way to have the subtitle line be the example sentance.