Ok, I'll admit first that I didn't exactly watch the whole video. 5+ minutes is way too long for my attention span, LOL. I watched a bit, fast-forwarded and watched a bit more.
That said, I'd also like to point out that 5+ minutes seems like too long for Maggie's attention as well. I noticed several times she started wandering away, she laid down, she was sniffing the floor a lot (either she was bored, or you were dropping crumbs?), etc. I don't know if you took breaks that weren't evident in my fast-forwarding through the video, but even so, she did look a bit fried by the end. So my first suggestion would be to perhaps time your sessions and keep them under a minute; train a minute, break for a minute; train a minute, etc.
I do like how you're quiet and not coaxing, prompting, cueing, or anything else to try to elicit the behavior; you're doing real shaping, just letting her explore and figure out what will get clicks. Very nice to see that!
When we train service dogs to push doors closed, we use a target. Not only is it an easy way to get them doing the behavior to begin with, it's also a very easy way to teach them to generalize the behavior to other objects and surfaces. While freeshaping like you're doing is working well, you might have to teach the behavior all over again when you start working on a different door. It takes a little longer in the beginning to teach them to touch the target, but in the end it really pays off if you need them to generalize.
I noticed one click towards the end where you clicked her for pawing. I know it was probably a mistake, but be very careful about that; pawing is incredibly self-reinforcing and one or two clicks of pawing will mean many sessions of training her to NOT paw. If you accidently click something you shouldn't have, you don't have to reinforce her; just wait for her to do another trial of the correct behavior. I know, it sounds crazy, but trust me, it works.
Though I will say, the fact that she pawed when previously she had just nosed, means that she's understanding that she needs to try something different; she's raising the criteria herself. While it's good that she's getting creative, it CAN also mean that she's bored with the behavior or bored with the session, and is trying to liven it up.
I also notice that the treats in your hands are distracting to her; try keeping the treats behind you, out of her sight, or perhaps in a container up on the shelf or something so that you reach for a treat AFTER you click. Having treats in your hands is also kind of a bribe: do the behavior and this is what you'll get! Which is not always bad, but that could be another reason she's getting bored with the session - even if you have a variety of treats, she knows which one is in your hands so she knows which one she'll get if she gets clicked. Varying up reinforcers - using food sometimes, toys sometimes, petting sometimes, etc. - will also help keep her interest and prevent her from getting bored with your predictibility.
