How to make the border (vignette) for the postcard

mirafoto,

You could make a feature request, I believe.

https://illustrator.uservoice.com/

You are welcome, mirafoto.

You can try to  copy the post into this (to the left),

https://translate.google.com

then set that source language (to the left) to English, then set the target language (to the right) to Finnish; Hyvää juhannusta translates to Happy midsummer the other way just fine, so you may easily get there or close enough.

Or, if you (have to) use a Swedish version, you need to choose Swedish of course;.

And in that case you can search for each English term here in the Help pages (empty search, just enter the term),

https://helpx.adobe.com/search-results.html?q=&scope=[%22helpx%22]&subscope=[]&limit=10&start_index=0&sort_orderby=relevancy&sort_order=desc&post_facet_filters={%22applicable_products%22%3A[]}

and then change the language by inserting /se right after .com in the URL, so it begins with

https://helpx.adobe.com/se/search-results.html?

Or you can try to look things up in under SV in this Polyglott kindly shared by Monika,

https://vektorgarten.de/illustrator-polyglott.html

mirafoto,

For a vanishing/fading to one side you can simply, and reversibly/editably:

1) Create a rectangle spanning the vanishing/fading area of the photo,

2) Apply a default linear Gradient going from black at the edge to white where the vanishing/fading is to end (you can set the angle of the gradient to fit whichever side of the photo you wish);

3) Select both the gradient rectangle from 2) and the photo and in the Transparency palette (flyout) click Make (Opacity) Mask with both Clip and Invert Mask unticked (in the main Transparency palette); the bits in brackets apply to older versions.

This will make the photo vaninsh/fade to full transparency = the white of the paper. On the Artboard you will see the Grid (when shown as in your screenshot) gradually show more and more through the photo towards the edge. There is no need to destroy the artwork by flattening transparency.

The (Opacity) Mask can be released and remade if you wish to make changes.

And you can (still) use a linked photo.

What if I need this effect only on one side of the image, to make the image vanish to white?
It is needed for the brochure, where the image takes only half of the page.
Currenty, I have to do it in Photoshop, but every time the design changes I have to re-do it, which is not acceptable.
Thanx a lot

You are welcome, mirafoto.

I am afraid you have to set the glow colour.