It is quite ugly when you first startup the maintable beta version of JabRef:

Plus, it won't memorize my modifications, either. That is, after I modify the size to a better one, it restores to the default again when I restart it.
This is better:

JabRef 4.2-dev--snapshot--2018-03-16--maintable-beta--2c2a302a5
Windows 10 10.0 amd64
Java 1.8.0_161
It is quite ugly when you first startup the maintable beta version of
JabRef:Plus, it won't memorize my modifications, either. That is, after I modify the size to a better one, it restores to the default again when I restart it.
This is better: