It sounds like you want to customize which screen Squid opens to by default. However, just so you know, you can already add shortcuts to open directly to a specific notebook. To do so, just long press on your device's homescreen and choose add shortcut/widget (wording varies depending on the device) and choose Squid's "open notebook" shortcut.
This is something we’ve been investigating since the app’s inception and we continue to investigate constantly. Syncing is a very difficult problem to solve, especially in regards to handwritten notes which can be combined with images and text. I don’t have any kind of ETA for when syncing will be supported, but rest assured this is a high priority for us. We appreciate all your feedback on this idea.
Sorry for taking so long to post an official response on this idea. Thanks Shiraz for suggesting posting an update/explanation. Please continue to provide your feedback!
Thanks for your feedback Peter. Yes, we wanted to merge similar ideas of additional notebook organization to keep the votes and comments in one place. This includes ideas for sub-folders/notebooks, tags/labels, etc. We're still investigating the best way to implement this and would love to hear everyone's feedback on the topic.
I agree that simple nested folders/notebooks is probably not the right solution. On Papyrus for Windows we introduced labels for notes (where a note can be part of more than one label).