Samba: Write access rights without read access rights possible?

TL;DR: Yes, it is possible. On Linux side, give your parent directory permission 300.

Longer explanation:

Note that for files, typical rwx triplet means permission to r = read, w = write and x = execute.

But for directories, such permissions have different meaning: r = browse directory, w = create or delete files, x = descend to directory or below it to access files or directories.

In other words, if you create directory without r permission, then user will not be able to browse it, however he will be able to access files or directories under that directory provided that filename is known beforehand (access means read or write files according to permissions assigned to files themselves).

Keep in mind that Linux permissions work on level lower than Samba permissions, and even if you edit your smb.conf to give apparently wider permissions, Linux level permissions will win if they are stricter than Samba permissions.

For example, this scheme allows to create directory that allows to create files and write to them, but not be able to browse list of those files or read from them:

mkdir dir
chmod 300 dir         # 300 = -wx------

Note that this directory must be created on Linux side - Windows client may not be able to create it with appropriate permissions.