See this post on actually pausing the sim. [HOW-TO] How to actually PAUSE the sim!.
There is a subtle distinction between pausing everything including time and pausing all action in the sim except for the passage of time. But you can bind keys on your keyboard to turn PAUSE ON and PAUSE OFF without pausing time. I’ve used the “P” key and “Ctl+P” for PAUSE ON and PAUSE OFF, which you have to bind in Options, Controls as detailed in the link provided just above by JvanE100.