What makes items appear in Nautilus sidebar and how to change it?

I'm on Bionic and the version of my Nautilus Filemanager is 3.26.4. I have quite a lot of different network folders defined in fstab: sshfs, nfs, smb, you name it. Plus a couple of USB drives that are plugged in almost constantly.

As you can imagine some of those are more important than others. So I'd really like to have a say in what Nautilus displays in the sidebar and what doesn't show up. Instead, Nautilus seems to have decided for itself what to display there and presents an interesting collection of items that is less than optimal.

I can't find out why rarely used items are deemed worthy to be displayed in the sidebar while important ones are banned to the vaults of "other places". And how I can change this.

Do you have any ideas or workarounds for this? Where do you control the behaviour of Nautilus' sidebar beyond a couple of bookmarks?