Hey Mike,

To change the cancel URL to the dashboard page, Refer below-mentioned steps.

1. Go to file path : root\components\com_payplans\themes\wireframe\checkout\default\default.php

2. Near line no. 219, find the below-mentioned code.

<a href="<?php echo $returnUrl;?>" class="no-underline">

3. Replace the code mentioned in 2 steps with the below-mentioned code.

<a href="<?php echo PPR::_('index.php?option=com_payplans&view=dashboard');?>" class="no-underline">

Do the above changes with template overriding, so your changes will not be lost on the upgrade.
Refer to the below-mentioned document for more details.
https://stackideas.com/docs/payplans/administrators/customization/template-override

Update us if you will have any queries.