A shortcut to open a property list for a form or object on a form when the property list is closed is to perform a double click on the item of interest. This can be quicker then performing a contextual click and then making sure that the Property List item is selected in the contextual menu.

Double clicking on the Form's area or the grey background will open up the Property List of the Form and double clicking on an object will open the Property List for the clicked object.

Related Links:
https://doc.4d.com/4Dv17/4D/17.1/Form-editor.300-4201259.en.html#108299