I think open does not work in this context. But @cgrunenberg would know better, of course.
You might be able to set a property of the top viewer window to the current record or something like that. I can’t check right now since I’m away from my Mac.
The open command is a standard AppleScript command but not supported by windows, tabs or records. Use openTabFor to open a new tab in the same window, in case of viewer windows having a preview pane you could also just set the selection if you want to reuse the current tab.
It’s really too few information about JXA for DEVONthink, meantime there are plenty of materials about JavaScript — MDN and so on — no problems with learning JavaScript.
selection (list, r/o) : The current selection of the frontmost viewer window or the record of the frontmost document window. ‘selected records’ relationship is recommended instead especially for bulk retrieval of properties like UUID.