Hello Balázs,
it is only possible to set Options and Sub-options for products, so depending on how customizable the products would be it may be necessary to create multiple products.
For example, separate products for a trailer with and without tarpaulin, adding to them options (for example Colors) and sub-options for each of them regarding castors.
I remain available.

For options, combine the different accessories as these change the price.

Enter the color in the sub-option as this normally does not change the price.

Example of 2 accessories:

• Trailer without accessories
• Trailer with accessories 1
• Trailer with accessories 2
• Trailer with accessories 1 and 2

Example of 3 accessories:

• Trailer without accessories
• Trailer with accessories 1
• Trailer with accessories 2
• Trailer with accessories 3
• Trailer with accessories 1 and 2
• Trailer with accessories 1 and 3
• Trailer with accessories 1, 2 and 3
• Trailer with accessories 2 and 3

Example of 3 extras with additional costs in the left selection, see

• 1 Trailer without extras
• 2 Trailer + tarpaulin
• 3 Trailer + castors
• 4 Trailer + blue paint
• 5 Trailer + tarpaulin + castors
• 6 Trailer + tarpaulin + blue paint
• 7 Trailer + tarpaulin + castors + blue paint
• 8 Trailer + castors + blue paint

In the right selection only the extras that are free of additional costs.

From 4 extras onwards, the selection list becomes very long, so that several products with 3 paid extras each are recommended. Or the extras are offered as separate products.

So that customers do not think that there are 2, 3 or more trailers when choosing, separate the number from the text with a minus sign, see

• 1 - Trailer without extras
• 2 - Trailer + tarpaulin
• 3 - Trailer + castors
• 4 - Trailer + blue paint
• 5 - Trailer + tarpaulin + castors
• 6 - Trailer + tarpaulin + blue paint
• 7 - Trailer + tarpaulin + castors + blue paint
• 8 - Trailer + castors + blue paint

With 4 paid extras, the left selection list would have 16 selection points and it would be quite complex to correctly determine all combinations.

And with 5 paid extras there would already be 32 selection points and the selection points could probably only be created with the help of the AI.

It will probably be difficult for customers if there are more than 3 paid extras in the selection list.

If there are many extras, it would be better if they could be purchased as extra products.

Alternative:

A separate page with the “Product Catalog” object that displays the respective trailer and the associated extras could be helpful here.

----- Separate page -----

Trailer 123

Lorem ipsum dolor sit at vero.

Trailer 123 ......................[ Buy ]

+ Tarpaulin .................... [ Buy ]

+ Castors ...................... [ Buy ]

+ Blue paint .................. [ Buy ]