@TimLittlefair: I have added this request to the tracker:
https://winscp.net/tracker/2041
You can vote for it there.

I too would like multiple selection of sites, precisely so that I can manage sites in folders and move them into and out of folders without having to move them one at a time.
I work with large numbers of devices on DHCP networks, being able to clean old site records into a folder without deleting them would be very helpful

This simulation is still useless as it requires me dragging and dropping between different folders and subfolders. I just want to use the native Windows (or Apple/whateer) ctrl, shift, or apple key to simply select more than one list item as is part of every application for the last 20 years.

You can "simulate" the selection of multiple site FOR DELETION AT LEAST by making sure the sites are in FOLDERS in site manager and then deleting the entire FOLDER of sites. I had to delete a whole bunch of sites. Fortunately they were all under a folder for that web host. I selected the web host folder, right-clicked and selected delete and I got rid of the sites that way. I wouldn't know how to edit / move sites doing this though. Hope this helps in some small way or gives you other ideas.

OK, will see if more users ask for this.

Yes, I want to select multiple sessions at once. Not edit.

WinSCP cannot do this.
The thread you refer to is about opening multiple sessions at once. WinSCP can do this already, but for a whole session folder only.

Regarding searching: Incremental search was added recently:
https://winscp.net/tracker/984

Btw, do you really need to edit multiple sites at once?

In Session (Site) Manager, I want to move/edit/delete multiple saved sites, but I can't select using Ctrl (or Shift) like in other dialog boxes. Am I missing something? I found an old thread (from 2007) that brought this up but was never answered.

In general I would love a more sophisticated session manager, with searching and so on, because I have about 100 stored sessions. Thank you.