The Shulchan Aruch 317:8 writes that it is permitted to make a bow on shabbos, to which the Rama adds that even if one will make a single knot below the bow, which is typical in the way we tie shoes, it is permitted. However, the M.B. (29) qualifies this by explaining that it is only permitted if the intention is to untie it that same day. According to Rashi/Rosh (see yesterday's page) it is permitted since it is not typically made to be a קשר של קיימא and the person tying it is intending to keep it very temporarily. Even according to the Rambam/Rif who consider every knot that may be a מעשה אומן to be an issur d'rabonon, the M.B. explains that it would not qualify as a מעשה אומן. However, if it is made to last for a significant amount of time such as the egged of a lulav that is made to last for the duration of Succos, the M.B. says that it is only permitted to do a bow without any form of knot underneath. The rationale is that a bow without any knot underneath doesn't even qualify as a knot, it is just considered wrapping. But when there is a single knot underneath as we do when we tie shoes, it is considered a knot, therefore if it is done for a significant length of time, it is assur d'rabonon according to Rashi/Rosh since it qualifies as being semi-permanent.
The M.B. then ends by writing that one can make two bows, one on top of the other, and concludes - וכן יש לנהוג. In my opinion this statement of the M.B. is somewhat misleading. It sounds as if he is saying that the making of what we call a "double knot" when we tie shoes, which includes a single knot, then a bow, then another single knot using the bow, is permitted. But in truth, I don't think that this is permitted.
The gemara explains that whether we regard a bow as a knot is a machlokes tana'aim. We pasken like the opinion of the Rabbonon who disagree with R. Yehdua and don't consider a bow to be a knot. What is the rationale for a bow not being considered a knot? It seems that the rationale is NOT that it is temporary, because a bow can actually stay for a significant amount of time. The machlokes would seem to hinge on the two rationales offered by the gemara 111b, in discussing whether according to R. Meir it would be permitted to make a bow. The rationale to permit it is that it can be undone with one hand, therefore it isn't considered a knot (although the Rabbonon would forbid a real knot even when it's loose and can be undone with one hand, the fact that for a bow pulling on one of the strings disassembles the entire bow, would be a rationale to permit it). The rationale to forbid is that it is still very tight, and able to last. The rationale of the Rabbonon who permit a bow by not considering it to be a knot is that it can be undone by simply pulling the string. Therefore, when one would make a double knot by using the bow to make a single knot, they are ruining the possibility of untying it by simply pulling the string, rendering it a real knot. This should then qualify as a knot on top of a knot which the Rama says we are concerned qualifies as a מעשה אומן and forbidden.
Based on this, after making a single knot and then a bow on one's shoes, one cannot make a second knot with the bow, even if there intent is to untie it within a day. The reason it is forbidden is that we are concerned for the Rambam that any מעשה אומן is assur, and since this resembles a standard double-knot which cannot be undone with one hand, it would be assur m'drabonon.
The M.B. who says that one can make a double bow would be speaking of a situation where one makes a bow on top of a bow, rather than using the first bow to form a single knot on top of it.