Crawling is very important. Opposition dexterity helps organize the brain coordination. It helps with true right or left sided dominance. True ambidexterity is one thing but most people simply have a confused dominance, as do I slightly. I can saw, hammer, bowl, catch, brush my hair, and other things with both hands equally well. Better on the left is: eat with fork, drink, bat, reach, carry, and type. Better on the right is: eat with spoon, cut with knife, write, cartwheel, throw, kick, and leap. I know that I am right handed idealy because I use scissors and brush my teeth only with my right hand. I am very slightly dyslexic. I have never had treatment and really don't need it. I can tell when things are backwards and I autofix rapidly. Thank goodness I am not color blind because sometimes the red and green light is flipped around. My is not all the time. When it is happening then I pay close attention and it may not happen for months at a time now that I am older. Mine is very tied to emotion and stress. It is worse when I am tired. Since my mid 20's I would notice that when I eat with my left hand I am in a certain mood. Distant, confidant, cocky, disconnected. My humor is different and I seem to be locked into the present of just a few hours. Sometimes I do not feel good and feel confused. On ocassion I have been able to force myself to eat the meal with my right hand as a right hander would eat and after a bit of emotional confusion would then feel fine, takes about 30 minutes, sometimes followed by a headache. I am telling all of this in a way that makes it look like a big deal but it's not. The emotional components are noticeable only to me usually. About 8 years ago after explaining most of it to my husband he can see it now. Now he is helpful in notifying me early in the situation and I fix it then instead of it lasting longer. I feel better functioning as a right hander. I no longer spend anytime writing, hammering, sawing, or bowling with my left hand. I try to eliminate others as well but eating and drinking left is harder because it is just so natural. My husband sits on my left side at dinners so I don't start with my left hand due to space.
I did crawl normally as a baby. However, I took dance, gymnastics, and twirling starting just before 3 years old. I was in class or practicing all the time. I became very good and it eventually it paid for school. Downside. I was always doing and trying to do things equally on both sides. It made for great talent but created other problems. I have 8 college degrees. I know, professional student and all. But they are in fine arts(paid for school, might as well get the paper) and science(human biology, anatomy). This topic came up on occassion. I already knew at that point that I had a problem and then understood why. So I started fixing on it. Skipping crawling is okay but you will need to do other 'cross crawl' activities and exercises with you child. Marching, kicking, hand to toe, hand to knee, elbow to knee, ladder climbing. All are correctly done with opposition. Left leg forward with right hand forward. Right leg forward with left hand forward. That's how you crawl, in opposition. That is how a dog and a horse trots. These activities don't have to be done ad nauseum, just some. Hopefully a few times a day in all totaling about 10 to 15 minutes a day. It works best if done at the age when they should be crawling. But cross crawl exercises even work with adults with dyslexia, they just have to spend more time. I think tap actually helps. For me I believe it was the twirling that messed with me. I twirled 2 and 3 baton and had to be good with my left hand. I injured my right hand pretty badly once and spent weeks twirling with just my left hand with my right hand in a brace. Sometimes this has its benefits: I am a good switch hitter and I can type about 90 words a minute.
You probably won't be able to find much on the topic. Medicine doesn't like to talk about anything that can be helped without meds. Remember, you need a dzs that is scarry and special and that only the pharmaceutical companies can help you with. If you try to take care of your own problems and don't depend upon the government then you are not being a good communist. I know this sounds jaded but the evidence is overwhelming.
ADD/ADHD are brain confusion/organization/firing issues. It wouldn't supprise me to find out that they are connected. I do not consider myself to be either of those truly. I can make myself sit still for anything, however, most people do things and talk too slow for my pleasure. I intentionally slow down my speech for most situations. I only know 4 people that can keep up. When we speak on the phone we fly. 2 of them know each other and we get together from time to time. Our conversations make no sense to others and we standardly interrupt each other without hesitation because the extra things being said are still heard and understood. We like it that way and it is somewhat humorous when other people walk away from the conversation they thought they wanted to join. 3 or 4 things going on at once is okay by me. I grew up doing homework watching TV. I have read homework while listening to lectures. I multitask well and am bored when too little is going on. I don't think that makes me ADD/ADHD. If it does then they are definately medicating a bunch of people unnecessarily. Of course if mom wants to sit on the couch and jr. wants to run around the house and play that doesn't mean that mom is lazy or jr is ADHD. Maybe it means that they are having different reactions to their malnutrition on a bagged, boxed, and canned food diet. And maybe jr needs a yard and a dog.
Anyway this is probably too much information, so sorry so long.
I wouldn't worry about the not crawling if the baby is naturally doing it themselves. But don't aid in the standing and walking. No walkers allowed, not the ones they sit in or walk behind. Put down a blanket and if the baby goes to something and pulls up, fine. Maybe you could bet down and crawl would help. The sit in, rolly, push with their feet, walkers are not good for the developement of their low back anyway. Too bad these things are given at baby showers and seem so convenient.
I hope you find some help or peace in here somewhere.
Pray for guidance and protection.