I guess at this point we are all running the dark with respect to the "gem bonuses" and especially the zumi "forget item" so you can learn a "new one"
Basically, without knowing what the other "bonuses" or "items" are out there, we don't know whether or not we should forget the current one we have.
Community please consolidate information here or on the wiki.
Zumi lv30 Metal Patch completion learned -> Frozen Patch (2hrs: increase Winter Chill dmg +20%, and duration 2 sec)
we also know from screenshot, we can learn -> Strike Patch (bonus ???)
lv45 learn -> Electromagnetic Shield (bonus ???)