We have a board which we use for internally found bugs and it would be interesting to have a “lock” on completing a task if it was deemed that it needs to be tested by QA to verify that it indeed has been fixed.
In this case person A (Dev) would be working on the bug report and should only be able to update the task, comment or assign it to other people. Once assigned to person B (QA) the feature gets tested again and if verified the task can be completed by them.
One preferable sub-feature would be to have a group have this “ability” and have the project owner fill in that group so that this can be scaled easily.