File Texture Manager is still my go-to. Not sure if it works with 2018 though.
It's still working in 2016.5 (though you do get that "Try It" warning every time). I will download the modified version -- glad it's still functional.
I'd also highly recommend Morgan Loomis's Python scripts for executing MEL and Python scripts within Maya. They create custom menus within the UI, making organizing and running external scripts like FTM massively easier than any other method (e.g. shelf buttons) I've found.
Shout out to Morgan!
Speaking of which, can anyone tell me why a line of MEL in my userSetup.mel file that worked in 2016.5 no longer works in 2017 and 2018?
The line is to call Morgan's script UI script:
python("import ml_toolbox;ml_toolbox.main()");
Previously putting this into userSetup.mel would auto load it at Maya startup. It no longer works this way, although if the same code is run from the script editor, it loads correctly.
I have another script in the same file to load Deadline client, which is working, so the file is being read.