Adding some settings to the dimension.json, like a structure list, gives an error. Here is the error that I had on the console register:

No key name in MapLike[{"structures":{"structures":{"minecraft:jungle_pyramid":

,"minecraft:endcity":{"spacing":10,"separation":5,"salt":10387313},"minecraft:village":{"spacing":15,"separation":4,"salt":10387312},"minecraft:ruined_portal":{"spacing":20,"separation":7,"salt":34222645},"minecraft:igloo":{"spacing":15,"separation":4,"salt":14357618},"minecraft:stronghold":{"spacing":1,"separation":0,"salt":0},"minecraft:bastion_remnant":{"spacing":15,"separation":2,"salt":30084232},"minecraft:desert_pyramid":{"spacing":15,"separation":4,"salt":14357617},"minecraft:nether_fossil":{"spacing":2,"separation":1,"salt":14357921},"minecraft:mansion":{"spacing":20,"separation":5,"salt":10387319},"minecraft:shipwreck":{"spacing":10,"separation":2,"salt":165745295},"minecraft:monument":{"spacing":15,"separation":2,"salt":10387313},"minecraft:swamp_hut":{"spacing":15,"separation":4,"salt":14357620},"minecraft:fortress":{"spacing":15,"separation":2,"salt":30084232},"minecraft:pillager_outpost":{"spacing":15,"separation":4,"salt":165745296},"minecraft:ocean_ruin":{"spacing":10,"separation":4,"salt":14357621}}}}]

I will provide the datapack that I used for this. Also tested this on 20w28a, but it gave more errors than 20w29a, I don't know why.