What is the nature of a withdrawal from Winglio, i.e. how should I report the money received from Winglio to my local tax authority?

If you are a regular user using the Professional plan, all withdrawals from Winglio balance are considered and paid to you as your secondary income. However, if you are a shareholder of the Winglio company then you can choose in each withdrawal request whether you want your balance to be paid out as a secondary income or dividend. In that way, you can optimize your personal tax duties in your country of residence.