Can I come back after cancelling?

Yes. Your data is kept, so restarting picks up your stores, your cost rules and your history rather than starting an empty account. Restarting begins a normal paid subscription immediately: the free trial is once per account, so a cancelled account does not get another one.

Between cancelling and restarting, Settings and Support stay open. That is deliberate, so you can always read what happened to your account and take your data with you.