It didn’t work, I don’t know why.

It works:

Probably reference the orange arrow.

It’s a huge .properties document where I’d like to translate each text after the = in another language.
There’s also things like that :

errors.openUrlError=Failed to open URL: {0}
errors.openDirError=Unable to open ‘’{0}‘’. Maybe it doesn’'t exist?
errors.reportErrorPreface=To report this error, please provide:\n\n

If you want to SELECT everything after the first = in a line

And, if that’s what’s wanted, please (OP) state WHY that is valuable to do…

1. Open find/replace form, go to Mark tab (or use Ctrl+M, assuming that shortcut is not already overridden).
2. Enter (?-s)(?<==).+, use the Mark all command.
3. All text on each line after the first = character will be marked.
4. Use the copy marked text command, and paste the copied text in a new file.

If you want to select everything after the first = in a line, that requires a scripting solution discussed here.