I am using rooted crDroid 9.5 custom rom and Gcam, I can't find an option in the system or camera settings to automatically save pictures and videos to the removable micro SD. I was thinking of a way to create a hard link between the DCIM folders using the terminal. If there is no way to do it automatically I was thinking of a script that moves all files to the removable micro SD card folder.
I entered:
ln sdcard/DCIM/Camera external_sd/DCIM/Camera
it returned an error stating that it cannot create hard link because it's a cross-device link.