I would love to know what action I can use to set a date in a field based off the date of another field.
To adjust a fields value use a Field action.
E.g Value of field_1 is 01/01/19. I wish to set Field_2 to a date that is equal to 01/01/19 + 28 days.
To modify a date you'll need to use the Format Functions. You can enable them under the Parameters tab of your auto action. At the bottom of that tab is explanation and examples for each format function. For your specific usage you'll need to use the "time" format function.
Also would like an action that will set a field with a word followed by current date/time. e.g. Value of field = complete 01/01/19 14:56.
You don't need format functions for this one. You can just use the normal Field action with either the Prefix operator or Set operator then substitute in your date.