Each time I use the "Vector library", I change the view scale of the icons to maximum, cause if I do not change it, is near impossible to see them. However, if I close Krita, I need to change again "icons size" scale, because they reset to minimum size

Please, fix it

Trying this with the 4.3.0 beta-1 release, the Vector Library docker does not remember the size of the icons. The Brush Presets docker does remember the size of the icons. The Layers docker remembers the size of the thumbnail images
You can raise a bug report here: https://bugs.kde.org/