Hi 
,
Not sure if the question has been asked before. Am I right to say that this is possible to run an advanced search on an organization-wide custom field (aka “custom fields in the organization library”) but this is not possible to run a search on project-specific custom field?
Thanks!
You are right here. As it stands, It is not possible to ran an Advanced Search for a Custom Field that is specific for a Project.
I know that this is not ideal, but a workaround could be to edit this Custom Field to make it available for the entire Organization (if it already exist you can add an underscore or hyphen). It will be then searchable and you can revert this whenever you need to.
Have a great Friday! 
Good workaround, thanks.
Hi @Natalia & @Bastien_Siebman I got stuck with this today… First question is there any update on this?
Second is some addition to the work around.
If you Save the Search as a report, then go back into fields and make that Custom Field project specific. The report still works… And actually allows you to change the value for that field as well without breaking it…
Not sure how this would go if you renamed the field but assume the search is pointing to the unique id rather than text.
Jason.