>>7873048
>-What are the medium or high quality social networks?
Honestly, X and Instagram are the only ones... it's bleak times.
If we're talking portfolio sites more specifically, then it's artstation. I can't say much about it, since I never use it, and don't particularly care for it - it's too sterile for me to appreciate.

>– how to put together and curate a professional portfolio?
Well, it depends on what you're going for, because even illustration has many sub-industries/niches.
The rule of thumb is quality over quantity (even just 10 pages), and making sure that each pages sort of flows into the next, you'll need to be thinking about the design of the entire portfolio, and not just the singular pages. If you have some b/w images, group them together, if the last b/w has a water theme, then the next page (that has colour) should also have a water theme... something like that... am I making sense?

Maybe try making several small portfolios, for each industry you're trying to enter.

>– what are editors looking for today?
Well, that's tricky to say, as it depends on the industry and the editor. Let's say this; if your work is very masculine and edgy, it's probably not suitable for teen vogue, now is it? So take a look at where you want to submit your work, and see if your work is actually suitable.
Maybe take a look at artists you know are currently doing well, and take notes on the features of their art, and try to replicate them to make your work more palatable to editors.

>– Frequent mistakes that lead to missed opportunities?
The most frequent one is probably never sending any cold emails. Just take the plunge.
A personal mistake that caused a missed opportunity for myself was not checking my email's junkbox... that still hurts.

>>7873289
cont.
>– how to stand out among hundreds of applicants?
Hard to say. Be better?
Actually, be professional. Artists are fucking notoriously unprofessional, to the point that they embarrass other artists.

>– What type of images add and which subtract?
What? We can't see your portfolio dude, how do we know?

>– How to present your work to publishers?
Try getting a literary agent, they would best be able to get it in front of publishers, at the cost of some of your pay - but given that's how they make their money, they'd be far more motivated to get you that contract.
Otherwise, just send in your work to where ever they say you can submit (or even if they don't say you can), and try to build your own audience to get publisher attention.

>– orientation for international markets.
Right to left, and change the font to wingdings.

>>7873289
>>7873291
Since not even OP wants to reply to you, I just wanted to thank you for producing two posts of actual answers to OP's questions.