I'm trying to make a game texture file, and the method I'm following involves decomposing an image into RGBA, replacing the Red and Blue layers with other images, and then recomposing. The guide also references functions which do not appear to exist in my version of GIMP, specifically the ability to have something automatically be pasted as a floating layer. I'd really appreciate suggestions, guides, or other information on any of the following: a method to move a floating layer created from Shift + Ctrl + L; a method to re-enable floating layers being the default paste option, or; a method for recomposing images which won't result in the "Cannot recompose: Specified layer [ID and layer number] not found" error that I've been receiving.

Might help first of all if you let people know what version of gimp you are using and your OS etc.

If you are following a tutorial from the internet it was likely created using a version before the one you have. Some things have been removed from gimp or given a new name.

By the way. Welcome to Gimp Chat