Hi John thanks for reaching out and apologies for the delay. Unfortunately there's no way to set default shape size. You can create custom shapes that are set to a particular size color font etc. and save it to your shape library to re-use. 

Is there a plan to fix this? 

Hi there! The method Sara described above is still applicable. You can also convert the document that contains your desired settings into a custom template by following the instructions here. You can then easily create new documents from the template and have your theme automatically applied. Hope this helps!

Hi! The link above no longer works. It would be so nice to be able to change the default box size; it's always way too big for my project when I try to use a line to lead to the next box it comes out massive. Thanks for your help!

Hey Joanne

Thank you for posting on this thread! Sorry for the link not working for you -- Here is a new link you can use. Let me know if this one doesn't work or if you have any other questions! 

Cheers