Is it permissible to place a small bag, like a handbag, in front of a worshipper in the mosque in order to pass in front of him?

The length of the sutra is an arm's length or thereabouts. This is an approximation, not a precise limit, because the Prophet, peace and blessings be upon him, measured it by the back of a saddle, and the back of a saddle varies in length and shortness. So, anything close to an arm's length is sufficient for covering oneself. As for its thickness and thinness, there is no limit; it can be as thin as an arrow or as thick as a wall. Accordingly, if the length of the aforementioned bag is an arm's length or close to it, then using it as a sutra is sufficient.