Making a knot is a melcha [action]. Which knots are biblical and which are rabbinical is questionable. Practically speaking, any knot made on another knot is prohibited even if it will be opened soon and any knot more the 24 hours is prohibited.

Chapter 317 Section 2

A strap of a shoe that is easily put back can be done on Shabbos.

Chapter 317 Section 3

A new shirt, where they used to tie the neck as part of the packaging from the manufacturer, is prohibited to be opened on Shabbos as you are fixing the clothes.