So you want to have three habitable planets orbiting a star and you want them to have orbits as similar as possible or even identical, so you don't have to do a lot of work making up different calendars for those worlds.
Maybe those worlds could have quite different orbits, but someone on this site will designed there different calendars for them for you.
Anyway, there is a blog, PlanetPlanet, by astrophysicist Sean Raymond. which has a lot of discussions of various fictional solar systems and their degrees of plausibility.
https://planetplanet.net/about/
It has a section called the Ultimate Solar System where Raymond designs solar systems with as many habitable planets as he can think of ways to make plausible.
https://planetplanet.net/the-ultimate-solar-system/
In the Ultimate Retrograde Solar System
https://planetplanet.net/2017/05/01/the-ultimate-retrograde-solar-system/
Raymond mentions a scientific paper which shows that it is possible to have planetary orbits closer together in a solar system that thought before. This makes it possible to have more planets orbiting in the habitable zone of the system.
https://ui.adsabs.harvard.edu/abs/2009Icar..201..381S/abstract
This is done by putting planetary orbits in alternating directions of movement. ONe planet moves in the prograde direction, the second in the retrograde direction, the third in the prograde direction, the fourth in the retrograde direction, and so on.
Raymond says, however, that a system of closely spaced planetary orbits with alternating directions could not form naturally (his occupation is modelling the formation of solar systems). Thus such a star system would have to have been created by super advanced beings millions or billions of years before your story.
I'm going to bed now my computer is acting up. But you really should read the following blogs.
In the next blog post: The Ultimate Engineered Solar System.
https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/
Raymond mentioned a scientific paper:
https://ui.adsabs.harvard.edu/abs/2010CeMDA.107..487S/abstract
Which claims that a bunch of planets, up to 42, could share a single planetary orbit if they were equally spaced. And Raymond says he has run similations showing that such a ring ofplanets could have stble orbits for billions of years.
And naturally, with his desire to create star systems with as many habitable planets as possible, Raymond speculated about several concentric rings of planets in the habitable zones of stars, each ring orbiting in the opposite direction to the rings in the next inner and outer orbits.
He created a system with six orbits of 42 Earths each for a total of 252 earths in the system, if all orbit in the same direction. With counter rotating rings of planets, Raymond got a system with 8 rings of 52 Earths each for a total of 416 planets in the habitable zone.
Of course the queston only asked about three habitable planets sharing a similar or idendical orbit.
Maybe EMS will happy to have even more than 3 habitable planets sharing the same orbit in their fictional star system.
But maybe the writer has a story planned that requires three and only three Earth like habitable planets sharing the same orbit. Since the minimum number of planets sharing the orbit has to be seven, that will leave at least four other planets in the orbit which have to be eliminated from the plot for some reason.
A molecule with chirality means that its mirror image is different from it. like a right human hand is different from a left human hand. Many ammino acids have chirality. And I think that animals can onlydigest organic materials with the proper "handedness".
If that is the case, there could be three planets in the orbital ring where the organic moleclules have the proper "handedness" for the lifeforms in your story, and four or more planets in the orbit where organic molecules have the opposite "handedness" and where life forms with opposite "handedness" biochemestry can live.
Or possibly three of the planet in the orbit have surface temperatures similar to Earth's. And possibly four or more planets in the orbit are "snowball Earths" covered by planet wide icecaps. Possibly there are liquid oceans below the icecaps, and possibly life, even intelligent life, lives in those oceans.
Or possibly the planets sharing the single orbit don't all have to have the same mass. Maybe three have a mass similar to Earth's and are habitable for humans and lifeforms with the same requirements. Maybe three are much smaller than Earth and are not habitable for humans, but do have lifeforms, possibly including intelligent life, on them. Maybe three are more massive that Earth and have surface gravities over 1.25 or 1.50 that of Earth, and no Earth lifeforms would want to live on them, but they do have life adapted to higher gravity and maybe intelligent life.
And there is another post, "Cohorts of co-orbital planets":
https://planetplanet.net/2020/11/19/cohorts/
where Raymond suggests that a ring of co-orbital planets doesn't have to be complete, there be a set of co-orbital planets in a arc segement of the orbit.
Raymond discusses the stability of various configurations, including cohorts of three co-orbital Earth like planets.
So unless you want to go with more than three habitable planets sharing the orbit, you should go with a set of three Earths sharing an orbit, spaced by 20 Hill radii along the orbit.