Is it possible to spawn an explosion at a specified grid coordinate, so that when a player steps on a certain trigger script, the explosion will spawn and play each frame at the designated coordinate?

I do see a section in the manual for FSM that mentions explosions: 

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Enemies and Decorations

EXPLOSION name radius - creates an explosion with a name and radius where name is name of explosion sprites. Sprites must be place in Data/Sprites/Effects.

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But I'm not sure that's what I'm looking for. 

They can also be reproduced by creating dummy enemies that bomb the moment they are generated.

First, create a dummy enemy who self-destructs upon death(Explosion radius is set in the editor) and his FSM file.

Use SETVAR to set a variable at the beginning of state CHASE, and then use that variable in JUMPIFEQUALS to move to state DEATH.

Finally, generate them in a specific location with a script.

This way, when the script is activated, the explosion can occur at any coordinates.