"could henceforth" is a correct and usable phrase in written English.
It can be used when referring to something that will occur in the future, or to imply that something will now be done regularly in the future. For example: "We agreed that we could henceforth meet once a month to review our progress."
Curtis aimed instead to penetrate to their cause, and to suggest a perspective from which we could henceforth begin to look.
He was given the job of formulating a set of criteria that could henceforth be applied to all Open courses and so bring a certain uniformity to the champion test.
The bathroom bill was drafted after the superintendent of schools in Fort Worth announced, in April, 2016, that transgender students could henceforth use the rest room or the locker room that corresponded to their gender identity.
What happened last week was an announcement by city officials that restaurants with sidewalk cafes could henceforth install portable natural-gas heaters and thus extend the weeks or months when a diner might comfortably — in terms of temperature, that is — lunch or sup outside.
The increased understanding of the capabilities of 3DP in dosage form design could, henceforth, accelerate pre-clinical testing of new drug candidates in animal models.
With a click of a National Security Agency mouse, Wikileaks.org could henceforth display a c. 1996 "url not found" message.
Sir Ian said that Britain couldn't henceforth produce actors of the stature of Ms Dench because "the current generation of actors won't develop into good middle-aged performers because they won't have been able to live from their work".
In other words, even saying asalaam aleikum was out of bounds, though Pakistan has no other common greeting.Ahmadis henceforth could not call the faithful to prayer.
The leader of the Greens, senator Christine Milne, called on Abbott to "pick up the phone" to try to calm down the row, saying he could promise that "henceforth this won't happen".
This act of establishing a particular estate as bookland, so that it could be held henceforth on these privileged terms, could be performed only by the king, in a royal assembly; but the diploma itself served hereafter as the title-deed for the land in question.
The genes of this pathway (which will be called the p-coumaryl alcohol biosynthesis pathway henceforth) could have been present in eukaryotic ancestors predating the origin of some or all of these groups, and lost in lineages in which the pathway is absent.
