Updated: March 23, 2018
The proverbial Linux bootloader - GRUB - and its TNG guise - GRUB 2.0 - is a highly customizable thing. Only the domain of its tweakability is reserved for expert users, who do not shy away from the command line. If you want to fiddle with the bootloader and its settings, you can. My two tutorials explains all the bits and pieces in gory detail.
For less knowledgeable users, the path is less obvious. Arguably, one should not dabble in GRUB if they don't feel comfortable. But say you want to change the background picture, the default entry, the timeout, maybe another setting or two. There's no reason why you should know the entire mechanism to be able to do that. Well, you should, for other reasons. Now, if you do want to make small changes, you're in luck. GRUB Customizer at your service.
Get the tool
GRUB Customizer is available with its own PPA for Ubuntu-based distro flavors, meaning the different variants of Ubuntu, Linux Mint and then a few others. Now, it is not the only available such utility; distros like PCLinuxOS and openSUSE also offer graphical frontends for managing bootloader sessions. But here, we will focus on GRUB Customizer specifically and what it can do. The first step is to install it:
sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt-get update
sudo apt-get install grub-customizer
Run the tool, start playing
Once you launch the Customizer, it will spend a few seconds scanning your system to figure out exactly what you have. In my case, a complex multi-boot system on my Lenovo G50 machine (seven distros plus Windows), it took almost three minutes for the probe to complete. You then get a list of all the entries.
GRUB Customizer did display all but one system - it did not see openSUSE with its BTRFS setup. I've noted this problem many times before. So there's something tricky about this filesystem that makes the Ubuntu OS probe gimp.
Now, you have the option to rearrange entries, move them up and down, remove them, edit them, or add new ones. Some expertise is required here, equivalent to the command line games. But the real elegance is making the remaining chances relatively easily, in an intuitive way. You can also manage general settings, as well as what the bootloader menu looks like.
The program is quite simple to use - relatively. You can also change the system environment, save your current changes - this will write the GRUB configuration to the disk, or install GRUB to MBR. I did not see any option on setting up UEFI. Maybe this is implied and/or automatic, but I am a bit confused by the MBR option as it potentially limits the choices. There's a tiny bug here - if you click Quit in the environment setup window, it will exit the program, and you will have to start again.
GRUB Customizer is an innocent little addition that should serve well in your Linux toolbox. It does not interfere with how you normally do things, and if you like the command line, you can completely ignore it, even if it's installed. If you're not in the mood to manually handle configuration files, you can make changes through its interface.
I like it overall, but I'd like to see some kind of novice/expert separation, where the former prevents catastrophic changes - although you can revert them, which is nice - and there are a few bugs, too. One, BTRFS. Two, the environment quit niggle thingie. Three, is UEFI explicitly supported, me wonders, and if so, this needs to be clarified. All in all, not bad. Worth testing and exploring. Thanks to JP for his suggestion. Take care, and happy Linuxing.