"Companion plants" is mostly nonsense. Not as if plants have their arms around each other. Interplanting early, short-season crops in the same beds as later maturing crops is a way to conserve space, but that's not about the plants liking each other. One can argue that deep taproots help break up the sol for other plants, but that's an issue only if the soil is poorly prepared. Insect management can benefit by keeping plants that attract certain insects away from other plants, but that's sort of irrelevant in a small garden. Legumes provide nitrogen to any other plants. Some plants (e.g. corn) can be used to support other plants, but that's just in place of poles or trellises.

That being said, small-stature plants do best if planted on the sunward side of large stature plants., to intercept sunlight better.

If by 'companion' plants you mean the idea of plants 'liking' each other you can ignore it. Just put your plants in the best place for them taking into account soil, sun, height and season of growth and length of time they will be in position.

I think grouping plants by cultural requirements is another way of 'companion' planting - that is, those needing more water, or shade tolerance vs. more sun. Some things like lettuces and other greens can benefit from some shade from taller plants in the heat of the day.

Reread the OP's post. They are asking about the spacing for non-companion or incompatible plants. And that is very much a real thing!! There are classifications of veggie plants that just do not play well with others.

Most sites do not specify spacing requirements.......only that certain plants should not be planted adjacent to each other. Alliums and various Solanaceae seem to lead the pack........

https://www.gardenia.net/guide/do-not-grow-these-plants-together

https://www.marthastewart.com/vegetables-to-never-plant-together-8425391

I tended a large vegetable garden for more than 50 years, I rotated the crops, of course, but, aside from that, found that they didn't care who was next door. All grew just fine:)

"but im struggling wigh the companion plants". The issue is companion plants.

With all due respect to Martha Stewart, I can't find any such info on this at any academic extension site or in any real research article. There IS self incompatibility, especially among Brassicas, which distinguish and reject self-pollination.

It's not just Martha Stewart. There are plenty of websites that state the same thing. Alliums (onions, leeks, garlic, etc.) are allelopathic with certain other veggies. And plants from the same plant family often will attract insect and disease issues that are more easily controlled if the plants are grown apart from each other.

If you don't believe this to be true, that's fine but I'm not going to research the issue for you. It is a very real thing and it is what the OP asked about.

I think it would help if the OP returned and explained exactly what they mean. The word 'companion' is problematic imo. It's sometimes expressed as certain plants 'liking' each other which is tosh. If there are genuine science based reasons for not planting near each other that's another thing. However, if you only have a small vegetable plot it's not really possible to segregate your plants and, ime, it's not the end of the world. For example, in a restricted space you can't grow your different brassicas far enough apart to stop mutual pests finding them. Another example, fennel self sows all over my allotment and I have never observed any inhibition of neighbouring plants.

Just to clarify our garden bed is one long one. so the whole length will be filled with veggies. in this case, melbourne australia we are heading into winter and i would like to grow all the way along in a more dense planting way instead of line planting like in farms.

if i am planting broccoli, cauliflower, radish and the herbs, onions garlic it is recommended not to plant them together as they font do well.

eg.

-Bok choy doesnt like radish kale rocket and cabbage

-cauliflower doesnt like garlic

-carrots dont like dill

so what i am asking is how far is enough space to plant dill away from carrots and parsley away from lettuce etc

as i dont have seperate beds and i want to grow a lot to last the season

Since Bok choy is also a Brassica, I see no reason why it 'doesn't like' other members of its own family.

Carrots and dill are also members of the same family, Apiaceae.

As to Cauliflower and garlic, this article actually recommends them as companions. https://www.bhg.com/cauliflower-companion-plants-7968718#:~:text=Allium%20plants%2C%20like%20garlic%2C%20onions,%2C%20aphids%2C%20and%20cabbage%20loopers.

Where is this information coming from?

Your bed doesn't look more than a metre wide, so I really don't think you have much choice about where to plant. More important then supposed 'dislikes' is the fact that some crops will be in the ground much longer than others so you don't want to disturb them with cultivating or pulling root crops around them. For example radishes will be ready within days whereas kale can take weeks. and some will be much larger and taller then others, so you don't want to shade the little ones. Again, kale can be a metre, radishes 5 or 6 cm.

I like to use the term companion planting. It's an umbrella term for me. It's a mixed bag of old tales and science. Tomatoes don't actually like or dislike dill- but dill is a good companion plant because it's an attractive plant for braconid wasps, a natural predator of tomato hornworms. This planting combo is now thought of as more of an intergrated pest management ploy than a companionship. Tomatoes can be a good companion to some lettuce. Not because of liking or not, but because lettuce can benefit from the shade cast by the tomatoes when it's hot out. Tomatoes and other nightshades don't actually dislike each other- they can be poorer companions because they compete for the same resources. Or sometimes because they can share a disease or bug predator.

So maybe don't think about companionship as liking or disliking. More like if there is a benefit or disadvantage to planting by each other. Does a plant suck up resources that will make another plant struggle. Can a plant benefit from the afternoon shade of another. If you have a pest is there a trap plant or host plant that can be utilized.

Yes, the advice cited seems backwards to what I'm familiar with. Grouping plants with similar culture requirements is one form of 'companion' planting, and can work out well, IMPE.

In fact, mixes of various varieties of the same crop - like broccolis, mustards, cabbages, etc. - are offered by many seed companies.

Plant taller plants like corn or sunflowers to act as natural dividers between incompatible plants.

That will not work. Tall plants will shade the plants each side and inhibit their growth. Corn uses high levels of nutrients and needs to be planted in blocks for good pollination. Sunflowers are genuinely allelopathic and stunt the growth of neighbouring plants.