RE: Adding extra chart cells after creation of dashboard
Hi partner,
You could edit the dashboard directly to add or delete components like charts or sub grid.
There are 2 ways to modify a dashboard.
For example I want to add a new chart in existing dashboard "Sales Activity Social Dashboard".
Way 1:
1.Go to Advanced Settings->My apps, since this dashboard is in Sales Hub, so I open the Sales Hub app designer.


2.Select "Dashboards" and find the dashboard in dashboard list.

Click the edit icon to open the dashboard editor form.
3.Now you've entered the dashboard editor form, here we could modify the existing dashboards as we want.
Click on "Char" to add a new chart. For example I want to add "Accounts by Industry" to this dashboard.


Back to app designer, Save and publish.

We could see that the new chart had been added to the dashboard successfully.

Way 2:
Go to Advanced Settings->Customizations->Customize the system->Dashboards.
Select the dashboard you want to modify and double click to open the dashboard editor.

The rest of the job is to edit the dashboard in the same way as above.
You could also refer to the following docs.
https://docs.microsoft.com/en-us/dynamics365/customerengagement/on-premises/customize/create-edit-dashboards
https://docs.microsoft.com/en-us/dynamics365/customerengagement/on-premises/customize/configure-interactive-experience-dashboards
Hope it helps.
Best Regards,
Leo