First of all, I have to say I like the spell.
I'm against adding abilities like that. The command card slots are limited enough, many custom maps use five hero abilities plus maybe backpack icon etc. and the extra icon won't fit there. Maybe you could replace the summon ability with the shoot ability, and when the orbs are used, give the summon ability back.
This is unnecessary since the unit has locust. You can set collision size to 0 in object editor.
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Unit - Turn collision for (Last created unit) Off
In Nether Bolt Load, you are loading stuff and then you do <Is caster alive> check. But you don't need all the stuff if the caster is dead.
Unit group leak:
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Unit Group - Pick every unit in (Random 1 units from PosTargets) and do (Set Target = (Picked unit))
add
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Cusom script: set bj_wantDestroyGroup = true
before that line.
These checks should be right after "remove unit from group" action:
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If (All Conditions are True) then do (Then Actions) else do (Else Actions)
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If - Conditions
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(FloatingBolts is empty) Equal to True
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Then - Actions
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Trigger - Turn off (This trigger)
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Else - Actions
In Nether Bolt Slide, you calculate Point[3], but you don't necessarily need it.
I'd modify the tooltip a bit. Using "you" in a tooltip isn't a good idea.
I'm puzzled as to why you'd name the ability v0.01, since clearly this isn't v0.01. The rules state that only "finished" spells should be uploaded (meaning v1.00).
The effects are nice and the coding is good in general.