Having a global variable and using pick by variable-contents is a bit simpler but you could also get a bit more advanced and store the UID and/or variable via array or dictionary. My head's a tad fuzzy atm, so I think it's more efficient (cut out the middle man) by storing the UID directly to an array/dictionary, if you want to go the more advanced route.
Dictionary (for the picking by UID action): Dictionary.Get("VariableName")
Array (same): Array.At(0)
(be sure to set the dictionary key or array to the UID before hand on creation, though, that may be an easy mistake to forget to)
I'm pretty sure the inside of Array's At follows a 0 or 0,0 or 0,0,0 format depending on array size. (i.e, just zero for only 1d arrays)