The grammatical index of Warder’s Introduction to Pali lists ten references for the optative tense. It’s first mentioned in Lesson #14 of 30:
The optative (or “potential”) (sattamī) tense is used for any hypothetical action. It may be translated by “should”, “would”, “may”, etc. …
p 86, beginning of sub-lesson
The range of meaning of the optative includes a mild form of command or a strong injunction, as well as requests, invitations, wishes, possibilities, suppositions, and hypotheses.
The hypothetical meaning is by far the most usual (cf. meanings of future, Lesson 10). …
p 87, 4th & 5th paragraphs
In the Saṅkhitta Sutta of the Aṅguttara’s eights, we find the optative tense employed in the context of eight training injunctions that follow (qv. yato) some degree of sammā samādhi.
What is particularly interesting here I think is that what appears to be a conservative rendering we have here on SuttaCentral obscures a difference in conjugation between the verbs “to train” and “to develop”:
Then you should train yourself thus: ‘Good-will, as my awareness-release, will be developed, pursued, handed the reins and taken as a basis, given a grounding, steadied, consolidated, & well-undertaken.’ That’s how you should train yourself. When you have developed this concentration in this way, you should develop this concentration with directed thought & evaluation, you should develop it with no directed thought & a modicum of evaluation, you should develop it with no directed thought & no evaluation, you should develop it accompanied by rapture… not accompanied by rapture… endowed with a sense of enjoyment; you should develop it endowed with equanimity.
https://suttacentral.net/en/an8.63/5
The root text has sikkhitabbaṃ for “you should train” and bhāveyyāsi for “you should develop”.