Seems like this issue is persisting into 1.18.1. I'm new to these forums so I hope that I am not breaking any rules, but I'll share the workaround that I came up with. I don't think that this issue is going to be resolved, unfortunately.
Although you cannot save a Marker armor stand to a structure. You can save armor stands with any tags to structures. If you save an armor stand with a tag such as markerTag, then you can add the Marker tag after the structure has been loaded. In this case, I would run a command like /execute as @e[tag=markerTag] run data merge entity @s {Marker:1}
Tyson Beltran
Seems like this issue is persisting into 1.18.1. I'm new to these forums so I hope that I am not breaking any rules, but I'll share the workaround that I came up with. I don't think that this issue is going to be resolved, unfortunately.
Although you cannot save a Marker armor stand to a structure. You can save armor stands with any tags to structures. If you save an armor stand with a tag such as markerTag, then you can add the Marker tag after the structure has been loaded. In this case, I would run a command like /execute as @e[tag=markerTag] run data merge entity @s {Marker:1}