ugh this is so frustrating that i have to ask this in forum.
when I received the quest 'to new heights' from Patrik in the dragonbone value, he told me to grapple up to the watchtower.
so the button for the grappling hook was blinking, but there is no associated keybind for it (maybe because I have slightly customized keybind). I tried to target the watchtower, and then pressed ALT so i could use the grappling button, but that does not work. I then checked in keybindings to see if I could assign it a new keybind. I could not find it.
then I tried dragging the grappling hook icon to one of my main item power tray slots -- the grappling hook disappeared completely (as if I discarded it), and now I cannot find the grappling hook in my "useful items" inventory.
I abandoned the quest and was able to pick up the quest and a new grappling hook by speaking with Kavatos and then Patrik again.
but what do I do to assign this a keybinding?
ugh so frustrating.
 oops - i figured it out. i feel so stupid. sorry for the post. but i guess i should ask if there is an easy way to reassign this a different keybind?