Steps to reproduce:
1. Open project
2. Select sampleTexture file from Assets
3. Check Inspector window's Texture import settings
4. Notice that "Format" field for Default is inactive

Expected: User is allowed to select the Format for default settings

Actual: Format field is inactive

Reproduced on: 5.5.0b6, 5.5.0b8, 5.5.0b9
Not reproduced on: 5.3.6p7, 5.4.2f1

Note:
It is possible to change format for individual platforms.