Add assignee automatically

Go to Custom Fields for cards.  Here you can add update triggers for fields used on cards. For example:

Syntax:

Add assignee automatically when a card is moved to another column:

if(FIELD_0001=='Step 2',FIELD_0005=Currentuser('Assignee'));

if(FIELD_0001=='Step 4',FIELD_0005=Currentuser('Assignee'));

Empty assignee field when a card is for example moved to a waiting column:
if(FIELD_0001=='Step 3',FIELD_0005=nil);

Cards switching between boards

Syntax for Moving" Card between boards (Workflow A and Workflow C):

Adds "Step I" for Workflow C when Card is moved to Step 3 in Workflow A:

if(FIELD_0001=='Step 3',FIELD_0003='Step I');

When working on board with Workflow C:

if(FIELD_0003=='Step IV',FIELD_0001='Step 4'); --> "moves" card to Step 4 of Workflow A
if(FIELD_0003=='Step IV',FIELD_0003=nil); --> "removes" Card from Workflow C

Workflow Streams

The following streams have been set-up in this example:

Triggers in action (video)