There are some home automation systems that work that way, but smartthings is not one of them. Instead of deactivating a motion sensor, you use filters to tell smartthings to ignore the reports from that sensor during specific times or conditions. It’s just the way the architecture is designed, but then, most battery operated sensors don’t have a way to turn off anyway, so it makes sense.
As far as pressure sensors, there are lots of discussions in the forum about those, it’s pretty straightforward. You just get any standard pressure sensor Mat (these are dumb) and then connect it to a device that can communicate to smart things, typically an open/close sensor with dry contacts. 
See the following thread (The topic title is a clickable link)
And this list of the kind of dry contact devices you can use:
FAQ: List of devices with dry contact input from external sources
You might also find the following thread of interest. Although the thread is old and you might use a different selection of devices these days, the basic ideas and approaches still apply:
Finally, there are a couple of pressure Mats and sleep monitors that have an Ifttt channel, so that’s another possibility. Several community members use the Withings Mat this way:
https://www.amazon.com/Withings-Nokia-Sleep-Temperature-Compatible/dp/B078Z1B34S
.
I will add that at our house we found it wasn’t any combination of automated monitoring that would produce the results we wanted, particularly since I have an 85 pound dog who likes to get on the bed.
So instead I put a motion sensor on side of the nightstand facing the bed. As I get in or out of bed, it’s very easy to just slide my hand so that it will trigger the sensor, but nothing else does. So it’s still on demand rather than fully automated, but it’s really easy to use and gives me full control over when to use it. 