[[Reconstruction:Proto-Indo-European/-yéh₁-|-yéh₁-]] not in [[:Category:Proto-Indo-European verb-forming suffixes]], then [[Reconstruction:Proto-Indo-European/-éh₁yeti|-éh₁yeti]]?

Reverted because it doesn't form verbs (stricto sensu). If that, then Reconstruction:Proto-Indo-European/-éh₁yeti shouldn't be cathegorised either in Category:Proto-Indo-European verb-forming suffixes?

But that suffix does form verbs.

So -yéh₁- is for declension? And -éh₁yeti for deverbal verbs?

The optative is part of the inflection of verbs, yes, at least by late PIE. There are some indications that it was originally a derivational suffix too, though, but it was integrated into verb paradigms as the optative mood in all languages, so the PIE sitation is not reconstructable in all details.

The -éh₁yeti suffix is basically synonymous with -éh₁ti, it formed stative verbs from roots or (perhaps later?) adjective stems.

OK, I simply took it from the definition "of the athematic stative verbal suffix" for -éh₁yeti. Shouldn't be -éh₁yeti better defined then as "1) Creates stative (or durative) thematic verbs from ¿(?perfective¿)? roots. 2) Creates stative (or durative) thematic verbs from nominals." like -éh₁ti, or "Thematic(-producing) variant of -éh₁ti,"?

Perhaps just {{synonym of|-éh₁ti|lang=ine-pro}}?

We have already that, in Reconstruction:Proto-Indo-European/-nós and Reconstruction:Proto-Indo-European/-tós, but they have exactly the same definition. In this case they should be different but parallel.