With this script you can use other image manipulation programs (like darktable, ImageJ, etc.) to create masks for GIMP, that have features that GIMP does not have.
How to use
Select the layer you want to add a mask to, open a grayscale or black and white image with this script, and easily load the file as a mask.
Sorry, I can’t read Python but it seems like 'Saver As" is different than the standard GIMP “Save As” which was left in place. I’m old and easily confused and find explanatory text helpful.
Saver will show up in your File menu as Saver and Saver as…
It goes back to Gimp 2.8 times when Save and Export were, for very good reasons, split. This caused much controversy from users who thought Export was an unnecessary step.
That is where Saver comes in, exports, overwrites, no other warnings about saving in Gimp .xcf format.