Hi @carterprine ,
Do you want to assign tasks to current user by clicking a button?
Could you tell me the task gallery's Items?
I've made a similar test for your reference:
1)the task gallery's Items:
Planner.ListTasksV3("NC88FLrSUkxxxx","33022910-a3xxxx").value
//"NC88FLrSUkxxxx" is my plan id
"33022910-a3xxxx" is my group id
Planner.ListTasksV3 is used to list tasks based on planid and groupid
The result will have id field, which is task id.
2)insert a button inside the gallery
set the button's OnSelect:
Planner.AssignUsers(ThisItem.id,User().Email)
If you click the button, you will assign the specific task to current user.
You could use Planner.ListMyTasks().value to check current user's tasks.

Best regards,