Hello Callum, thank you for your answer.
After launching AD following your instructions I can create styles again but everything is pixelated: for example if I draw a vector pattern that I export as png and then import this png to create a style, everything is pixelated, the png and the style. I didn't have this problem before and I can't find where the problem comes from.
It seems that the problem has solved itself? I just did several tests, still with the same settings I used before my problem, and the pixelization has disappeared (except in case of excessive zoom, which is normal), the results are now as expected. Another computer mystery!
All I have to do is reinstall my brushes, styles and assets backups.
Thank you again Callum for your answer.