Can you add entries to fstab with a GUI in ubuntu?

On Ubuntu you can edit your fstab using the gnome-disk-utility. From the terminal run gnome-disks or type Disks from the dash. Select the disk then the partition, from the Option menu select Edit Mount Options.

KDE Partition Manager is an alternative to gnome-disk-utility , it can be installed on Ubuntu and debian based distro.

file, disk and partition management for KDE

Partition Manager is a utility program to help you manage the disk devices, partitions and file systems on your computer. It allows you to easily create, copy, move, delete, resize without losing data, backup and restore partitions.

Partition Manager supports a large number of file systems, including ext2/3/4, reiserfs, NTFS, FAT16/32, jfs, xfs and more. Note that to gain support for a specific file system other than ext2/3/4, you should install the corresponding suggested package.

Partition Manager is based on libparted (like gparted) and makes use of the KDE libraries for its user interface.

To install KDE Partition Manager:

sudo apt install partitionmanager