You can define custom fields with Gtmhub that go with tasks. By default, Gtmhub will store info from the built-in fields. However, you can easily add more fields to suit your needs.
Check out this general guide for Custom Fields.
Idea for task custom field
Task custom field
Let’s say you want to add a Priority custom field for your tasks. You can create a custom field for tasks with this information:
Programmatic name of the field. This field has several requirements: must be unique, must be lowercase, can be letters only, has to be between 4 and 12 characters
UI Label: Priority
This is the name of the field that will be displayed in the user interface. There're no requirements here
Description: Identify which priority level this work takes
A hint to users on how to use this field
UI Selector: One option list
Type of the field depends on the type of information you want to store in this field
Target type: Task
Once you've created your Priority custom field, you can use it when you're working with your tasks.