Steps to Reproduce:
- Open the Bookmarks Library (either Control+Shift+B or Hamburger Menu->Library->Bookmarks->Show All Bookmarks)
- Click Organize->New Bookmark
- Click the "Show all Tags"/"Hide" toggle a couple of times
When the tag selector is expanded, the dialog grows to accommodate it. The behavior I observe when the tag selector collapses, however, is inconsistent. Sometimes the dialog shrinks to its original size. Other times the dialog remains approximately the size it was before the tag selector was collapsed. See the attached GIF.
This behavior has been reproduced on macOS and Windows 10.
I came across this when working on Bug 1585482. When I apply the (unfinished) patch, the behavior no longer seems to be inconsistent. Instead, it never shrinks to its original size when the tag selector is collapsed. Oddly, I also see the same change in behavior if I open the Browser Toolbox to inspect the dialog (whether or not the patch is applied).