My Better Portals - portals disappear sometimes, from time to time, and it doesn’t bother me too much; I can just reopen the portal.

But the End exit portal only opens when the dragon is slain.
The problem for me is, I had build quite a lot on the End island, and resummoning the dragon with End crystals will destroy a lot of my builds.
I tried placing the end_portal blocks, all at the same time, with command blocks in the portal frame, but that didn’t work.
Neither did killing an Enderdragon summoned through commands.

Is there a way to restart the portal manually via commands? Such as, spawning in the entity that acts as the portal?