I’ve noticed that my org-todo window takes up half the vertical space (with empty space at the bottom) rather than just the four rows of todo tasks that it normally does. This only happens when the org-roam backlinks window is open. I haven’t been able to find a similar report, but I may not be using the best search terms.
I am unsure what you mean by the org-todo window. Detailed (confusing) discussion here: org mode - How to control where the org todo keywords buffer displays? - Emacs Stack Exchange
These emacs variables can help perhaps:
(setq split-height-threshold 0
This video explains it in depth: Hey Emacs, Don't Move My Windows! - Customizing display-buffer's behavior - YouTube
Sorry for being unclear. I mean this window.
That thread seems to talk about the right kinds of things. I wish I knew why the org-roam backlink window altered the behavior of the todo window.
That is indeed the org-todo window. Did you try setting the threshold variables?
It seems to be a complex subject - the video I linked is almost an hour.
Yes, I did try setting split-height-threshold to 0 with no effect.