I always testing (Run Action) each action, one-by-one.
But it doesn’t works with variables in a sequence. You can just select on sequence level “Run Action” otherwise the previously defined variables will not initialised.
As second option you define the (global)-variables on the top of Actions. But in this case, you cannot testing (Run Action) the lower actions one-by-one. The only one solution for testing will be the trigger initialisation.