Does cancelling a LL restart your clock? I see mention of booking anything to keep your stack and then modifying it later, but I would think cancelling and rebooking something else/another time would mess things up. Is there a certain order you have to do things in?
Cancelling an LL
clears your eligibility clock, making you eligible to rebook immediately. But when you do rebook,
that will reset your eligibility timer to 2h (or the expiry time of the LL you just booked, whatever is sooner.)
So say it's 10:45, you're holding an LL for 2 pm, and will be eligible to book a second LL at 11:00. You can wait until 11, book a second LL,
then cancel the 2 pm and immediately replace it with another, leaving you with two booked. OR you can cancel and replace the 2 pm right away, but your eligibility timer to book a second will now be reset to 12:45, unless you book an earlier LL and either tap into it, cancel it, or allow it to expire.
In other words, if the primary goal is to start a second "stack", you should wait.
ETA: When people say "book anything to keep your stack", they mean that if you are currently eligible to book, you might as well do it, even if you might modify it later. Eligibility is a binary concept - you either are, or you're not. So yes, if, at 11 am, I book an LL, and then an hour later I change my mind and cancel/rebook, I'll push my eligibility timer out. But I'm not any worse off by doing that than if I just waited until noon to book that new LL in the first place. And if I
don't book, and something else happens in the meantime that would make me eligible to book (eg. I tap into an existing LL, or another two hours pass), then that 11 am opportunity to book a second LL is, in effect, permanently lost. I can still book another LL anytime, but I only have one, when I could have had two. HTH.