How do I make a 3-in-one room?

You can define zones by placement of furnishings or you could build zones with screens, curtains, or other dividers.

A pressing room? Do you mean for ironing (pressing clothes)?

You could incorporate all three of your needs into your laundry room. You could use on of these for hanging freshly dried and ironed clothes. https://amzn.to/2VxnpKV

May I suggest that you have an ironing board that folds up to the wall. Storage shelves, various depths in between to take different sized clear totes or baskets. Shelves above your laundry appliances. You will need some kind of table so if you had a portable one made you could place over the appliances if you need to do any sewing or cutting work or a folding table could also be placed on a wall which comes down when required for folding clothes, etc. Check out the Houzz.com site for visual ideas.

How you do this relies the actual space you have and time you have and your actual size.

I would recommend you start with an 8'×8' room right off of the master, with a Combo Stacking Washer/Dryer and possibly some shelfs and a rod for hanging clothes (like a walk in closet).

Even if you are a huge person, Worst comes to worst in that large area is that your ironing board has to stick out the door some, which even in that outcome is still not bad because you have your hang up clothes easy to hang up and end up ironing less.