uci set luci.apply=internal
uci set luci.apply.rollback=60
uci commit luci
3 Likes
I feel kinda stupid now. I've searched for the term 'fallback', not 'rollback', when I tried to figure that out myself using 'uci'. 
And that little drop-down is not available in 18, so I still miss that one until upgrading to 19. Actually my fault, sorry about that!
I tried to upgrade several 18-boxes to 19, but WLAN-configurations get partly destroyed on dual band devices, when keeping the configuration (three radio devices in the web ui, when there are only two physical and second radio config applies to the phantom radio device). So it's not doable remotely in cases, where boxes are using STA-mode as WAN link. 
Thanks for the time reading and for the screenshots!
Manuel