Nested mappings are not allowed in compact mappings - Working on .yml for mcmmo

Question

I'm having trouble with adding modded items into my mcmmo plugin which usses .yml files to read those.

Boots:    
    Travelers Boots: tconstruct:travelers_boots
        Repairable: true
        Repair_Material: minecraft:copper_ingot
        Repair_Material_Data_Value: 0
        Repair_Material_Quantity: 1
        Repair_Material_Pretty_Name: Copper Ingot
        Repair_MinimumLevel: 80
        Repair_XpMultiplier: 1.0
        Durability: 130
    Plate Boots: tconstruct:plate_boots
        Repairable: true
        Repair_Material: tconstruct:cobalt_ingot
        Repair_Material_Data_Value: 0
        Repair_Material_Quantity: 1
        Repair_Material_Pretty_Name: Cobalt Ingot
        Repair_MinimumLevel: 150
        Repair_XpMultiplier: 1.2
        Durability: 390
    Slimeboots: tconstruct:slime_boots
        Repairable: true
        Repair_Material: minecraft:slime_ball
        Repair_Material_Data_Value: 0
        Repair_Material_Quantity: 5
        Repair_Material_Pretty_Name: Slimeball
        Repair_MinimumLevel: 250
        Repair_XpMultiplier: 1.5
        Durability: 546
    Chocodisguise Boots: chococraft:choco_disguise_boots
        Repairable: true
        Repair_Material: chococraft:chocobo_feather
        Repair_Material_Data_Value: 0
        Repair_Material_Quantity: 1
        Repair_Material_Pretty_Name: Chocobo Feather
        Repair_MinimumLevel: 75
        Repair_XpMultiplier: 1.0
        Durability: 2600    

When starting up server it spams alot of "Nested mappings are not allowed in compact mappings in line x column y"

****I'm using Notepad++ for editing the file.

I tried changing the spaces at the start of the columns, checked my notpad++ program and put a check to the option of auto swapping tabs into spaces. (read in a forum that might help)

Ran it through YAMLlint the YAML validator and it says:

"Nested mappings are not allowed in compact mappings at line 2, column 22 Implicit keys need to be on a single line at line 2, column 22 Nested mappings are not allowed in compact mappings at line 3, column 21 Implicit keys need to be on a single line at line 3, column 21 Nested mappings are not allowed in compact mappings at line 4, column 26 Implicit keys need to be on a single line at line 4, column 26"

^Hope this will help troubleshooting!

Thank you for reading! I'm hoping someone can tell what the problem is.