Steps
1. open a project (ideally lots of textures)
2. switch color space in project settings > player settings > other settings

Expected: cancel button is usable or not shown (and a warning before switching color space)
Actual: cancel button is not usable and no warning that it may be a slow operation for first attempt

Note: big project required to notice the issue of texture reimport time

Repro: 2020.2.0a21