This was technically added in 1.88 (see 1.88 release notes).
But since I made some extra improvements to it since I'm making the post now.

ShowDebugLogWindow() is also accessible via Demo->Tools->Debug Log or Metrics->Tools->Debug Log.

It has options to enable logging of variety of events.
Useful e.g.:

• You have issue with focus or active id being taken away.
• You have issue with popup closing.
• You have issue with windows being undocked.
• You want to visualize submitted input events.
• You want to visualize clipper steps etc.
• etc.

From today a new functionally was added to it and to many places in the Metrics windows: if you hover an ImGuiID identifier (formatted as 0xXXXXXXXX) it will automatically to visually locate the item if the item still exists:

Also see wiki page for more tools:
https://github.com/ocornut/imgui/wiki/Debug-Tools