I’d love to see the NINJAL-LWP dictionary added (I think it classifies as dictionary?). You can look up words and it tells you what particle the word is most commonly used with, what construction it comes up in most, what conjugation is the most common (when looking up verbs) and so on. And for all these it shows you the sentences where it got the construction from. I think they scan lots of blog posts and texts from other websites. It’s all in Japanese, but has been super useful for me so far!
When checking if someone had proposed it before, I found a post talking about this website where you can check for compound verbs, their meaning, and examples. You can also only look up compound verbs with only one of the parts.