it really depends what kind of impediments do you have:
– Is it something that have been identified during the retrospective?
=> You can create stories (with type technical and maybe a tag) as action to fix the impediment
– Is it something that block someone of the during a sprint?
=> You can display a “block sign” on a task and create urgent tasks to unblock the thing
Also you can use the retrospective rich text to display them on the project dashboard using bold / checkbox etc..
=> Always the last retrospective is shown
Let me know if it helps