The truck has no canopy. It has several states though:
Model: armies\soviet\vehicles\us6_truck\us6_truck
State machine name: us6_state
Values: base, katyusha, supply
State machine name: supplies_loaded
Values: empty, partial, half, majority, full
These states can be found with the worldbuilder (C:\Program Files (x86)\Steam\steamapps\common\Company of Heroes 2\WorldBuilder_CoH_2.exe)
This has a NIS function which can show a list of states for each model.
Edit: This video might be more helpful than the guide: https://youtu.be/5V62qgEu3Ww?t=428 (7:05 - 9:00)
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#Steam AliasWL%Streak
- 1.693240.743+13
- 2.43965.871+3
- 3.447154.744+9
- 4.315119.726+11
- 5.675103.868+1
- 6.317168.654+4
- 7.10551.673-3
- 8.10929.790+10
- 9.297134.689+4
- 10.279149.652+2