I've added selvedges to many many quilts that called for neutral strings, and I have an ongoing project with wider colored sides that doesn't know yet what it will be, so far just 6.5" blocks.
When my mother had dementia and lived with me I could never actually think, so I set up an old machine by her chair where she could see me and sewed strings by the 100's. those have gone into many projects too. a lot for sashings.