Susanna, good for you! The desk/bookcase look very handy.
I've been keeping a binder for each machine, with manual or manual copy, notes about attachments, needles and usage, history of the maker and whatever seems important all together. Putting the pages in clear sleeves keeps them neat, and additions can be made anytime in any order. The hope is also that compiling this information will make it easier for someone who adopts the machine in the future.
Have fun with your machines,
Dianne in Colorado