How do I search for "?"

[troejgaard]

The same is true for any file.
I don’t know if “problem” is the right word… It’s a consequence of balancing multiple competing factors. If DEVONthink indexed every possible character, I assume the standard search wouldn’t work as well as it does—and it wouldn’t have the same amazing speed.

@troejgaard

When you search, DEVONthink doesn’t go through each file individually. To keep search performant, DEVONthink extracts (indexes) information from your database items to a so called “search index”—under the hood, in the internals of the application—and searches that. This is common; Spotlight and Google does the same.

Not all special characters are indexed. You can’t search for those that aren’t. (The manual lists the symbols ‌$€£¥%§ as indexed on p. 88, Windows > Main Window > Search Pane)