Help Please!!!
When @jacky93sims explained to me how editing the object in CRES works, without needing to move the object in the 3D program, which opened my mind to possibilities, she gave me the link to the Numenor tutorial and through this, I learned how to finally reduce tiles and consequently finally understand the tutorial recommended by @hugelunatic, because when I tried three months ago, unfortunately I hadn't managed to do it.
Yesterday I tried again and I succeeded, I learned how to add new tiles.
For example this playmat, originally the object is 1x1, but the object I converted I made so that it is 3x3, so that the slot where the newborn is placed is in the middle (1x1), but the sim cannot get close to the object to place the newborn, even though I have unchecked some boxes in the footprint in CRES.
Editing the BHAV so that there is an intersection between the object and the person causes the sim to intersect the object, which I don't want, so I added new blocks.
Anyway, does anyone know what I should do so that the newborn can be placed on the playmat without being blocked and also without passing through the object, please?

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For that object, adding 4 tiles would've been enough (covers the object). Looks like 9 tiles makes the item inapproachable.

If it's a deco object and your plan is to add the other (usable) item on top of it, it's definitively too big. You could probably make the item not interactable, but that would defeat the purpose, I guess.

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Before making 3x3 (9 pieces), it was 2x2 (4 pieces), but the place (slot) where the newborn doesn't change regardless of whether I edit the CRES, even the footprint that should be on the tile (0,1) where the bear is doesn't work, it persists in staying in the same position (0,0), so I added more pieces, but the sim doesn't approach or cross the carpet, even if I edit the footprint in CRES.
Here is what I am referring to when the slot where the newborn is placed and also the footprint that does not change, even though I edit the CRES and it is the footprint on the tile (0,1) where the bear is :

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You can specify allow intersection for each tile separately. It can be done by giving them each a separate function - init, and then calling a shared common. If you define an OBJf - "Allow Intersection", you can specify intersection for each tile even more detailed based on various conditions, for example, the active person can intersect, but others cannot. See how it is done on the Food Stand, Soccer Net or similar objects consisting of multiple tiles where some can be walked over.

After the object was extended to more tiles, and you want to refer to say, the center, it may have a diffent multi-tile subindex number before and after extension.

Andif it doesn't work, you could scale down the blanket a bit, and just use the original 1x1 footprint/size. Both the blanket and bear looks a bit oversized compared to the baby anyway (Looks like it's more sized for the TS4 infants, which are almost TS4 toddler-sized. TS2 babies are quite small in comparison).

Thank you to everyone for taking the time to help me.
Jacky93Sims walked me through what I needed to do.
It was necessary to edit the x and y axes of joint 0 in CRES so that the mat fit correctly into the 4 pieces and the groove to place the baby was in the middle.
I was also advised to edit the routing slot so that the sim doesn't sink into some parts of the legs when squatting to place the newborn.
The only final problem that occurs is that the child “falls” to the floor when clicking on the option to place the child on the mat, it takes one or two more attempts to achieve this. This occurs after editing the routing slot.