since version 3.5.0 it is possible to use sumUp within your Issue Matrix custom fields!
sumUp has to be manually activated for Issue Matrix in the sumUp Global Settings!
Activating the calculation row
To use sumUp with Jira Core, make sure it is activated in Global settings under Manage apps. Otherwise, the buttons will not be displayed.
You can use the toggle switch to enable or disable the gadget.
To permanently activate it, click the lock icon.