SC2Mapster

Copy and paste it from another unit.  That's what I do.  Go to a unit with a custom status frame that you like (my personal go-to is "Alarak - Void"), then click on their actor, find "Custom Unit Status Frame" and copy that field onto the "Custom Unit Status Frame" field of the unit you want to change.

Update: I found out how to get it to work.

For the summoned unit, look at its Timed Life Effect when it summons a unit. It should have a behavior for the duration of the unit.

Edit that behavior’s “Stats: Kill Credit +” field where it says “Value” with a drop down box, and select “Caster”.

Tldr: I changed the behavior “swann - Turret Timed Life” -> stats: Kill Credit + -> Value -> Caster

The purple aura is a SwarmHeroGlow actor.

In order to remove it, you have to find Dehaka's actor and take a look at his events field. Delete the actor event that applies the glow and you should be good to go.

Most of the co-op abilities make use of triggers. This includes Blaze's Enflame ability. Just look through the Co-op trigger folder until you find the one that says "data utilities". The Enflame trigger is somewhere in the Tychus folder. 

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Power Visual Prodigal engineer under actors.

setting basic art model to none will remove the field entirely.

Cheerio!