In most cases clearing the web browser's cache fixes the problem with missing PoE menus in the SwOS.
If it has not fixed it in FireFox browser, go to History menu and do a search by typing RB260GSP IP address in search bar.
Then select RB260GSP SwOS entry, open options with right click and set “Forget This Site” to delete it from history.
Appreciate the info. I'll try this later to confirm (I'm not near the switch at the moment). However this is the first time I've accessed the switch from any browser. I'd be surprised if they all need to be cleared in order to get all of the options in the switch interface.
I contacted MikroTik support and was informed that PoE output is only provided in passive mode, and is intended for powering other MikroTic devices (especially switches, and access points). So it's a mute point for me since I'm attempting to power a Cisco VoIP phone. But I'd still like to see the PoE tab when I access the switch!