The field "Sample Type" restricts the plate type to have samples only of the specified sample type, i.e., if no sample type is defined for a plate type,
samples of any type can be on a plate with this plate type.
If the sample type is specified, solely samples of said sample type are allowed on a plate with this plate type. In the case a sample of different sample type
is assigned, e.g., a sample of type "Biological Sample - Sequencing" is assigned to a plate with a sample plate type "Library - Illumina",
a child sample of type "Library - Illumina" is created.
By pressing on save, you are redirected to the platetype/details screen, where you may later edit or delete the plate type.