Cloud FlowOrchestrationIntermediate

Trello Approval List Workflow

When a card is moved to an Awaiting Approval list, the flow launches a Power Automate approval to the assignee/owner, writes the decision as a card comment, and moves the card to an Approved or Rejected list. Adds governed, auditable approvals to a Trello board.

TrelloApprovalsOffice 365 Outlook

Unique name

FlowLibsTrelloApprovalListWorkflow

Publisher

FlowLibs (flowlibs)

Version

1.0.0.0

Components

5 env vars + 1 cloud flow

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What it does

Overview

This flow adds a governed, auditable approval step to a Trello board using the Power Automate Approvals engine. When a card is moved into an Awaiting Approval list, the flow launches an Approve/Reject request to the configured approver, writes the decision (and the approver's comments) back onto the card as a comment, moves the card to the Approved or Rejected list, and emails the approver a confirmation.

Why it matters: Trello has no native, auditable approval with assignment and outcome capture. This wraps cards in the Microsoft Approvals engine so every decision is tracked, attributed, and recorded on the card itself.

Ships Off - turn on by authorizing the three connections and setting the four list/approver env vars.

Why you'd use it

Use Case

Teams that run requests through Trello (content sign-off, purchase requests, change requests) want a real approval gate tied to a list, with the decision recorded back on the card. Move a card into the Awaiting Approval list and the approver gets a Power Automate approval; the outcome is written to the card and the card is filed in the Approved or Rejected list automatically.

Step-by-step

Flow Architecture

Card Enters Awaiting Approval

Trello - OnNewCardInListV3

Polls (every 3 min) for cards entering the list bound to flowlibs_ApprovalListId.

Initialize Config & Card Context

Initialize variable (x7)

Binds board, approved/rejected lists, approver, and the triggering card's id, name, and URL.

Start Approval

Approvals - StartAndWaitForAnApproval

Launches an Approve/Reject request to the approver and waits for the decision.

Check Approval Outcome

Condition

Branches on outcome == Approve.

Approved branch

Trello + Outlook

Comments APPROVED (with approver + comments) on the card, moves it to the Approved list (UpdateCard_V2), and emails an approval confirmation with the card link.

Rejected branch

Trello + Outlook

Comments REJECTED (with approver + comments) on the card, moves it to the Rejected list, and emails a rejection notification with the card link.

Solution config

Environment Variables

Schema name	Type	Default	Description
flowlibs_TrelloBoardId	String	REPLACE_WITH_TRELLO_BOARD_ID	Board the trigger polls and the comment/move actions write to.
flowlibs_ApprovalListId	String	REPLACE_WITH_AWAITING_APPROVAL_LIST_ID	The Awaiting Approval list that triggers the flow.
flowlibs_ApprovedListId	String	REPLACE_WITH_APPROVED_LIST_ID	Destination list when approved.
flowlibs_RejectedListId	String	REPLACE_WITH_REJECTED_LIST_ID	Destination list when rejected.
flowlibs_ApprovalDefaultApproverEmail	String	approver@yourcompany.com	Approver who receives the approval and outcome email.

Auth dependencies

Connectors & Connections

Connector	API name	Actions used
Trello	shared_trello	OnNewCardInListV3 AddCommentToCard UpdateCard_V2
Approvals	shared_approvals	StartAndWaitForAnApproval
Office 365 Outlook	shared_office365	SendEmailV2

Note — All connections are referenced as solution connection references; the flow is portable between environments as long as a connection is mapped at import time.

Tweaks & variations

Customization Guide

Almost every realistic variant of this flow can be implemented by changing environment variable values. A few cases require small edits inside the flow definition — those are called out explicitly below.

Per-card approver routing: Replace the static approver with a member-to-email lookup (ListCardMembers -> map member id to UPN) so each card routes to its owner; fall back to the default.
Multi-stage approvals: Chain a second StartAndWaitForAnApproval for high-value cards (e.g. gated on a label) before the move.
SLA / escalation: Wrap the approval in a Do until with a timeout, or add a parallel reminder branch that re-notifies if not actioned within N hours.
Re-entrancy guard: Set an interim label (e.g. In Review) on first pickup and filter it out so a card lingering in the list is not re-submitted.
Richer audit: Log each decision to a Dataverse table or SharePoint list alongside the card comment for reporting.

Helpers & literals

Key Expressions

The flow is intentionally light on Power Fx / WDL gymnastics — the heaviest expressions are the branch-name concatenation and the approval outcome check. They are listed below in the order they appear in the flow.

EXPR.01Outcome

The approval outcome.

workflow definition language

body('Start_Approval')?['outcome']

EXPR.02Branch test

True on approval.

workflow definition language

equals(body('Start_Approval')?['outcome'], 'Approve')

EXPR.03Approver display name

Who actioned the approval.

workflow definition language

first(body('Start_Approval')?['responses'])?['responder']?['displayName']

EXPR.04Approver comments

Reviewer comments captured from the approval.

workflow definition language

first(body('Start_Approval')?['responses'])?['comments']

EXPR.05Target list (single-action form)

Resolves the destination list from the outcome.

workflow definition language

if(equals(body('Start_Approval')?['outcome'],'Approve'), variables('varApprovedListId'), variables('varRejectedListId'))