Symptoms
When using Copy teams channels for a team with a OneNote tab, ShareGate Migrate displays the following warning:
The OneNote notebook referred by this tab was not found at the destination. This can happen if the notebook was inside another channel that was not copied. The tab was copied without its content, it will have to be manually setup at destination.
Details
Note: When a team is made, a default OneNote notebook is created along with the other Microsoft 365 services. It will have the name Team-name Notebook (Default team notebook).
A team's default notebook exists in the site assets of the associated SharePoint team site. When you copy into an existing team, you will need to manually set the location of the notebook in Teams.
Copying a notebook will work differently if you copy a channel into an existing team within the same tenant or if you copy a channel into an existing team within a different tenant.
Solution
Copy into an existing team - Same tenant
Open Teams.
In the destination team, select the copied channel.
Select the tab Source-team-name Notebook.
Click Set up tab.
In the Select a location for your new tab dialog, select the Source-team-name Notebook.
Click Save.
Copy into an existing team - Different tenant
In ShareGate Migrate, click Settings on the bottom-left menu.
Under General, scroll to Hidden items.
Toggle on Display system lists.
Close settings.
Click Copy.
Select Copy content only.
Click Connect.
Select the associated team site of the source team. Use the dropdown to expand the information.
Select Site Assets.
Click Next.
In Teams, locate the copied channel at the destination.
Click the Three dots menu button
in the top-right corner.
Click Open in SharePoint.
Copy the URL.
In ShareGate Migrate, paste the URL as the destination Site address.
Add your Authentication information.
Click Connect.
Select the name of the SharePoint documents folder.
Click Next.
Select the Source-team-name Notebook. Click Start Copy.
Follow the steps (1) to (6) above.