When you need to validate a task or series of tasks assigned to teammates, there are different ways you can set up the work flow, depending on how you prefer it to be
organized and shared with them. It all depends if the validation embeds or is embedded into a task or a series of tasks, and if you want the step shared or just for yourself.

Subtasks can be very handy for that purpose.

You can for example create a "master" task that you keep assigned to you and then create the subtask(s) that you want assigned to others from inside your task that you can review and that represents your own action.

Example 1:
TC is manager and needs some piece of work to be validated by her in the end.
She has assigned a task to BE so (s)he submits design proposals.
Once the design proposals submitted by BE, TC would like to validate them.
Here is how TC can set this up using a task that she keeps for herself, and creates a subtask assigned to BE:

Example 2:

TC's final review step can also be a subtask of the task assigned to your teammate:

Example 3:

From the task TC has assigned to BE, she can also use the "Create a Follow-up Task" action for her Review task. 

TC'S task refers to the task assigned to BE:

EXAMPLE 4:

Some work processes are in a sequence. So, once someone has done its part, the task is re-assigned to the next person in row who needs to make progress with the task. Unassigned subtasks can also be used so everyone can have a check list and knows what's next and who they need to reassign it once they've completed their part.

EXAMPLE 5:

Some teams also just @mention their manager inside the task so (s)he can review it and close but it usually means there is a unique task until the final review happens and it may remain listed in the to-do of the assignee who accomplished its part of the work. So I recommend on of the above.