Hope this is not too far OT, but it is DIY & is a problem that some
contributors to this group may have the knowledge to answer.

Dry cleaners often offer the service of putting permanent creases in
trousers. IMHE these last a very long time, surviving many ensuing
washes. However the only home crease treatments found in shops so far
are starch sprays for use during ironing and resulting creases
disappear very quickly (2 days or less).

Hence Q: how can you replicate by DIY the permanent crease produced by
dry cleaners?

If it matters the nub of interest is mainly a treatment for cotton
material rather than artifical fibres (polyester, terylene, rayon
etc).

TIA