There is a plug-in (python), named Word Art from b&p (bytes and pixels) that allows you to create different layers of font characters. Sort of a word cloud engine.
http://www.bytes-and-pixels.com/downloads/?did=13

I can confirm it works in Gimp-2.10 as well.

If you want to keep each font character layer consistent just choose 0 variation for all settings and every layer should be the same size and color. I always go with Black bg and white font color.
Type each character (for instance A - Z) vertically in the font name field. Here are my settings for A - Z.

[ Image ]

And you have to have an image open in Gimp for the plug-in to start. It will create a new image.

My results from these settings. Each layer is a different font face. I could have just chosen 1-26 for font range.
[ Image ]
The font characters do not center on the canvas so you will need to move them all to center and then crop all to content. There is a script for that also. I believe it is named Multiple Layer Actions.

Then just decorate each layer as you see fit. Just another way to create custom fonts in Gimp.