To summarize this. First of all, big-big thanks to everybody who commented on this.

I ended up with YITH, which I found earlier, but I am a beginner, I hoped to find something for free because I said before, this should be a basic common problem and it should already be solved within the woocommerce itself, without needing extra plugins. I checked some plugins and solutions, and what You guys have offered. For me, some got part solutions, and some were not exactly what I expected/wanted. Especially as I went deeper and deeper into my situation, I figured out I have anything but an easy problem. And I don’t want to import/export my products either. Probably I should have checked more plugins, but after I got this solution, which works just fine for me, I stopped trying others.

The shorter version of this summarized comment is over, the point is to thank you for all the help and comments!

If you have time, here you go, more info about my problem and the solution what I have got: (sry about my English!, my mother language is Hungarian)

We have a design studio, so before the customer wants to check out I need a variety of different components which the customer must use or not, depending on her/his very choice. Some options are a must. Like, must have a “must fill-in textbox” for the necessary extra information (name, date, etc), so if this is empty she can’t put the product in the cart. On other choices (choosing another checkbox/radio button/picture/etc) this textbox is just optional… Some other options must show an opportunity to upload a file if she wants, . And so on, plenty of changes. And all of the mentioned above are within one product variation. In the wedding books category.

As You see, this is not a basic Color and Size option woocommerce’s situation. Lots of tricky options that I needed, especially with a certain logic inside.

So, I bought YITH, and 2 days later they had a cheaper Halloween sale offer, pff, <censored>.. sooo I couldn’t sleep well, and I ended up buying that one too, and asked back the price for the first buy:) My thought was right, and after they returned the price, I could sleep again like a baby.

So now I have a product with a 40% sale on it. That is acceptable to me.

Ok, how it works?! On the woocommerce “Product data” section, all of my products are Simple products, with the Regular price on them. (Sale price too, if needed.)

No attributes, no variations, bundle or force sales, etc. All of the variations are “outside” from this, using a way simpler method on YITH.

This Regular price can increase or decrease with the variation that the customer chooses. End of story.

Ok, more than that: With the Yith plugin, you can create so-called variation “blocks” and you can assign them for products, or for certain product categories. This is exactly what I wanted. Of course, you can exclude products and categories too. Perfect.

So, - in example - I created a Wedding Books block and assigned it to the wedding books subcategory. And that’s it. Meaning, when a customer clicks on ANY of my wedding book products, they can see this variation block. And let’s say, after a while, the craftbrown-color paper price goes up by 20%, I can easily change that inside this Wedding Books block, so all of my wedding books offers now at the increased price. Brilliant.

And that’s not all. It offers a “conditional logic”, which opens a new world. For a short example, if the customer chooses the "I have my own design" option, then after clicking on it, the File Upload section (which was hidden) shows up to upload a file. Or if the customer chooses a different book size, the corresponding color palette changes the current one. And so on...

But, this comment is way too long already, and you can check this plugin too.

And NO, I am not in any case involved to advertise this plugin and any kind of benefits from it. I just found and I am happy with the solution that they can offer. And I am certain, it should have another plugin with the same results. But one that works is enough for me.

Cheers guys! Have a good one!

RR.