Add Honey-Dijon Vinaigrette ingredients to a jar with a tight fitting lid or bowl then shake or whisk to combine. Set aside.
Add potatoes to a large pot then fill with cold water and season with salt. Bring to a boil then cook until potatoes are tender, 10-15 minutes. Drain then return potatoes to pot off the heat for 5 minutes to help evaporate excess water.
Toss warm potatoes with 1/3 cup Honey-Dijon Vinaigrette then refrigerate for 1 hour or up to overnight.
Heat olive oil in a large skillet over medium heat then add onions and a dash of salt. Cook, stirring every so often until onions reach a caramel brown color, 20-25 minutes, reducing heat slightly if they start to brown too quickly. Remove skillet from heat then let cool slightly. Can be done a day ahead of time. Cool then store in the refrigerator.
Place eggs in a saucepan then cover tops by 1 inch with cold water. Bring to a boil, place a lid on top, then remove pan from heat and let sit for 12 minutes. Drain then plunge eggs into ice water or run under cold water for a few minutes. Peel eggs when cool enough to handle then chop and set aside. Can be done several days ahead of time. Cook then peel eggs and store in the refrigerator.
Combine marinated potatoes with caramelized onions, chopped hard-boiled eggs, bacon, and green onions with as much Honey-Dijon Vinaigrette as you like then toss to combine. Taste then adjust salt and pepper if necessary.
Notes
To enjoy as a warm salad, combine warm potatoes (do not refrigerate) with caramelized onions, bacon, and green onions then dress with vinaigrette.