GIMP 3.2.4 intermittently launches with a different (BEAUTIFUL), more compact interface and dialog layout

Hi everyone!

I am using GIMP 3.2.4 on Windows. Yesterday, after opening approximately 15–20 JPG images at once, GIMP unexpectedly displayed a noticeably different interface even though Help → About still reported version 3.2.4.

This was not simply a different icon theme or icon size. The change affected the interface throughout the application:

  • Toolbox icons were substantially smaller and more compact, with more tools visible at once.
  • Menus and dialog boxes appeared thinner, denser, and generally different from the normal GIMP 3.2.4 interface.
  • Color-adjustment dialogs such as Hue-Saturation and Brightness-Contrast used a different-looking control layout.
  • In Hue-Saturation, the R/Y/G/C/B/M color indicators appeared visually different from the normal fixed-size color swatches. They appeared to vary in size/length, giving displaying the relative amount of each color present in the image.
  • Adjustment controls also appeared more compact, with small arrow/numeric controls rather than the normal large slider presentation.
  • Even file-related dialogs, including the Save/Export interface, appeared simpler, thinner, and different from the interface I normally see.

After closing GIMP and reopening it, the alternate interface disappeared and the normal interface returned. I have been unable to reproduce it.

I have since tested or ruled out the following:

  • GIMP Theme: Default vs. System
  • Legacy vs. Default icon themes
  • Icon-size override
  • Single-window vs. multi-window mode
  • Toolbox tool grouping
  • Resetting GIMP preferences
  • Windows High-DPI compatibility/scaling override

None of these reproduces the interface I saw.

I would like to determine what caused GIMP to display this alternate/compact interface and, if it is an intentional interface mode, how to enable it again. I actually preferred the alternate layout because it was considerably more compact and appeared to provide more detailed controls and color information.

Environment:
Windows
GIMP 3.2.4
JPG images, approximately 4000 × 3000 px
Issue first appeared while opening approximately 15–20 images in one session

No one has had this, or knows what it going on?