As implemented in JENKINS-54635, it should be possible to configure an alternate approle path in CASC
location : line 24 of https://github.com/jenkinsci/hashicorp-vault-plugin/blob/hashicorp-vault-plugin-3.0.0/src/main/java/com/datapipe/jenkins/vault/jcasc/secrets/VaultAppRoleAuthenticator.java
".loginByAppRole(approle, approleSecret)" to be replaced by .loginByAppRole(<PATH>, approle, approleSecret)
reated https://github.com/jenkinsci/hashicorp-vault-plugin/pull/63
Sometimes it is faster to actually contribute code.
Fixed in https://github.com/jenkinsci/hashicorp-vault-plugin/releases/tag/hashicorp-vault-plugin-3.1.0