13.2 where is "Toggle Bookmark" key mapping?

I have not found in Toad options any key mappings to "Ctrl+Shift+0/9" or any bookmark functions in shortcuts.

The question have appeared because I can set bookmark using "Ctrl+Shift+1/4", but cant using, for example, "Ctrl+Shift+5".

Bookmark shortcuts are hard coded and not configurable.

Since you are not seeing any shortcut mapping in Toad's Options for Ctrl+Shift+5 you might want to check other running processes, in particular anything you have that might be globally hooking your keyboard. For example, I use a clipboard manager (ClipX) that hooks keyboard events and out of the box it was configured to steal a shortcut I commonly use in another application. I had to disable that shortcut in the clipboard application.

If you can't identify anything and you have another tool with configurable shortcuts try mapping Ctrl+Shift+5 to a command in the other application and see if it works there or if it's also broken as in Toad.

Can you right-click in the editor and still Toggle/go-to the bookmark (5)?

Also, since shortcut keys are configurable for many actions in Toad, could it be possible (though probably a long shot, I'm guessing) that Ctrl-Shift-5 is assigned to another action within Toad that is taking precedence? Might be good idea to do a quick check on the shortcut key assignments in the Toad Options base (View>ToadOptions->Toolbars/Menus->Shortcuts) to see if there is any action assigned this shortcut.

Lastly, @mstaszew,
I noticed that the bookmark shortcuts do not show in the master shortcuts list (because they are hard-coded?). But when I do assign a Ctl-Shift-# for an action in the Shortcuts list, shouldn't I receive a Conflict Flag? Or is it the case that, because the bookmark controls are hard-coded, there would be no conflict?

OP mentioned in first post that this is not the case.

If this is the case it's technically a conflict, but will not be reported. The conflict detection there just compares shortcuts to other shortcuts also shown in the list. Ideally there would be no hard-coded shortcuts and all would be shown in Options.

you might want to check other running processes
really, I have found it.
"Cloud Mail.ru", also may be screenshooter from mail.ru have this bag - even if screenshooter disabled in settings, program blocks this shortcuts at startup.