You can Engrave a Stele as many times as you want. This will only swap out the manual currently set on the Steel.

You can only Imprint from a Stele once per run. Imprinting will create a copy of the Manual currently on the Stele and consume it for that run. If you save after Imprinting a manual, you will not be able to reload and change your choice later down the line.

One tactic is to have an end-game save with a bunch of Manuals. Then you can engrave any manual that run has. Then you have a new run Imprint those manuals. Although you can only Imprint 5 Manuals at once, this increases the amount of options you have avaible.
This way, you have a rotating set of Engraved manuals available for any future run.

You can only carve the orange martial arts that you have already learned, and it has been cultivated to the highest level

Wrong. Only level 10 martial arts can be imprinted but it’s not limited to orange. Red martial arts are possible to engrave too :)
Just comprehend 2 orange martial arts level 10 on the fusion at the center of the stele and create your ultimate martial arts (then engrave it for your other runs)