Features used to implement the example

• Read fields from linked issues or sub-tasks
• Write field on linked issues or sub-tasks

Example: Sum sub-task's "Time Spent" (work logs) and add it to a certain linked issue

Issue type A is linked to issue type B. Issue A has sub-tasks and people log work at the sub-task level. When issue A is closed I need all work logged in its sub-tasks to be copied to issue B. Actually it has to be added since issue B may have work logged from other issues (Issue B is a summary of what is being logged at a lower level). I have been trying using virtual field Total time spent (minutes) in Close post function with copy parsed value and write to linked issues, but it doesn't work...maybe there is a conversion that I am missing.

It is possible to implement your requirements using post-functions Read fields from linked issues or sub-tasks and Write field on linked issues or sub-tasks, and virtual field "Total time spent (minutes)".

Use post-function Read fields from linked issues or sub-tasks with the following configuration:

Use post-function Write field on linked issues or sub-tasks with the following configuration:

Once configured, transition will look like this: