excogitate vs create mentally

excogitate and create mentally both are verbs.

Word	Noun	Adjective	Verb	Adverb
excogitate	No	No	Yes	No
create mentally	No	No	Yes	No

As verbs, create mentally is a hypernym of excogitate; that is, create mentally is a word with a broader meaning than excogitate:

excogitate: come up with (an idea, plan, explanation, theory, or principle) after a mental effort
create mentally: create mentally and abstractly rather than with one's hands

Other hypernyms of excogitate include create by mental act.

excogitate (verb)	create mentally (verb)
reflect deeply on a subject	create mentally and abstractly rather than with one's hands
come up with (an idea, plan, explanation, theory, or principle) after a mental effort