1.10.4.1198
It is reproducible.
No
If you cannot provide a sample document then please give an accurate description of the problem for example it should include most of the following:
Windows 10 21H1 with all patches, I7 mobile CPU with 32 GBytes of RAM and SSD
hardware acceleration is on
The problem is, that a JPG image 2848x4272 wos loaded, and I have 3 active filter layers (clarity on top of Noise reduction on top of Shadows & Highlights, all as sublayers of the imported image. If the filter layers are removed, export is fast. It seems that the program creates a hidden "merged visible Layer" first with no indication of progress and then stores this layer.
If I create a merged visible layer on top, this lasts approximately the same time, but with a progress indicator. If I then export the merged visible layer, it is fast, but only if I disable all layers below. I would expect, that an opaque merged visible layer with Normal blend mode should trigger a switch which would then disable rendering of all layers below. Since they are invisible anyhow.
In any case I expect the progress indicator of the export to move in the phase of preparation. Especially since this phase takes the larges part of the time required. Mybe you could have two phases:
Progress indicator for "Prepare for Export"
Progress indicator for Export (as now)
In the current state, the progress indicator is at 0 for 10+ seconds and then rushes to the right in 0.5 seconds