Thanks for sharing. For now there is no statistics or folder in Trengo that does this.
What we do ourselves, is attach a label to a conversation as soon as it is assigned by a Flowbot, see screenshot attached.
Later, when the Flowbot assigns or closes the conversation, we automatically remove this label by the use of Rules, and attach another one to the closed conversations by the flowbot, to measure how many there are.
If you need any help in setting this up, feel free to reach out to firstname.lastname@example.org where our Product Specialists can help you with this.