Searching for common words is always hard. But you can use Translation Strings | Discourse Translations to search for strings. It works quite well.
By default it does a fuzzy search within string keys and string values, which isn’t really helpful when you search for a single, common word like all. Searching for the exact word or phrase (case sensitive) will narrow it down a lot. Currently searching for "All" returns 19 results.
js.discourse_reactions.users_popup.all | Discourse Translations works, and it has a link to Crowdin. 