Tag nylon exists already, but I think it would be incredibly useful to have a TPE/TPU tag and a tag for all flexibles as a category.
EDIT: It has come to my attention that the tag flexible already exists. I still would like to see a tag tpu though.
flexible could be used together with the filament to indicate the question is about flexible filament, but I understand that it may be beneficial to have separate TPE/TPU tags (it saves a tag). Furthermore, there are also tags for pla, abs, pom etc.
I suggest to make 2 tags tpe and tpu where the TPU tag is a synonym for tag TPE.
From What is the difference between TPE and TPU Flexible Filament?
TPE = ThermoPlastic Elastomer
TPU = Thermoplastic PolyUrethane, which is a type of ThermoPlastic Elastomer
which is as 0scar has already stated, i.e. TPU ∈ TPE. It goes on to say:
Although technically classed under the ThermoPlastic Elastomer spectrum, the full name for TPU is ThermoPlastic Polyurethane. This isn’t especially new in industry, but until recently wasn’t commonly available in 3D printing.
However recently it’s growing a lot more popularity among printers. While on the surface very similar to TPE, but TPU 3D printing has some notable differences.
TPU is very similar in elasticity and other mechanical properties to TPE. Although it is very slightly more rigid, at Shore 94A-95A. This makes it a little easier to print in printers that don’t usually print the original, softer TPE 3D printing filament well, as the slight more rigidity is easier for the extruder mechanism to handle.
So they don't seem exactly the same. I dunno, I'm not sure. However, we apparently have the tags already, so that isn't a major issue anymore.
With regards to the synonym aspect: Are the questions going to to be the same, i.e. will the same issues happen to both TPU and TPE, or will TPU have special, particular issues? If the latter, then a synonym maybe isn't a good idea.
Regarding flexible, I wonder if it is necessary. Aren't we trying to reduce the number of filament tags? See Fixing the filament tags. If having flexible will help in this direction then all well and good, otherwise, maybe it isn't.
However, I'm not a filament expert. You can decide what you want to do and if you need me to do it, message me in chat or leave a comment.