Starting in Firefox 65, you can specify a fully qualified path (see r and cert4.pem in this example).

The Install key by default will search for certificates in the locations listed below.It is equivalent to setting the security.enterprise_roots.enabled preference as described in the Built-in Windows and macOS Support section below. We recommend this option to add trust for a private PKI to Firefox. Setting the ImportEnterpriseRoots key to true will cause Firefox to trust root certificates.Starting with Firefox version 64, an enterprise policy can be used to add CA certificates to Firefox. Using policies to import CA certificates (recommended) You can add these CA certificates using one of the following methods. This should be done early on, so your users won’t have trouble accessing websites. If your organization uses private certificate authorities (CAs) to issue certificates for your internal servers, browsers such as Firefox might display errors unless you configure them to recognize these private certificates. This article is intended for IT administrators who wish to set up Firefox on the computers within their organization.

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