Does the paid version of Genymotion support root access and allow writing custom certificates into the system directory?

Yes, the paid version of Genymotion supports root access and allows writing custom certificates into /system/etc/security/cacerts/.

Root can be enabled through the device property persist.sys.root_access. The available methods include:

• Checking Root Access when creating a device
• Switching it in Launchpad under System
• Modifying persist.sys.root_access through ADB or the HTTP API

After root is enabled, both apps and the command line can obtain root privileges. The system certificate installation example is to run adb root, then adb remount, then push the certificate to the system certificate directory and set its permissions to 644. For Android 10 and above, the system partition can also be mounted as writable after root, then the certificate can be pushed and permissions set.

The documentation example uses the directory /system/etc/security/cacerts/, as shown in Root Access and How to connect Burp Suite to Genymotion.