Unable to change dom.ipc.processCount

Firefox is slow on Android. Multiply reddit posts recommend changing dom.ipc.processCount to 32 and I've even seen Firefox community posts with recommendations of 4-7. I find that any of those settings help the performance over that of the default 2. The problem is a reboot, closing of the browser, etc resets the setting back to 2.

Is there any way to keep our custom dom.ipc.processCount setting on Mull browser?