How to log food properly?

The tare function on your scale is key. In a bowl set to 0 add your say 20g mushrooms hit tare then add say 30g onion ECT.
Or log all the veggies as say mixed veggie

You can enter the components individually then save it in Quick Tools as a Meal. Then the next time you make the omelet, you can add the "Meal" to your Food page, and change the quantity or individual ingredients if they are different..

Vegetables are pretty low cal, so getting a bulk amount would work fine, too. Like "1 cup mixed vegetables" would be close enough.

I have many meals that I have entered into either "Meals" or "Recipes" and I can use them and tweak them if necessary.

I have been doing this for a number of years. Started with Weight Watchers and then move to MFP. For me I have found that logging low/No calorie ingredients is time consuming and painful. And the more painful the quicker I will stop doing it... Therefor I do not log spices or most vegetables. If I have a salad for lunch, then I log the dressing, croutons, tuna, etc that has calories. Same thing for recipes. If I eat a pound of spinach or cauliflower then I will never notice those 20 calories because I will not be hungry all day and probably will not hit my 1600 calories for the day anyways. Using this approach I am able to stick to tracking (mostly) and the number on the scale still goes down on Monday morning :-).

My advice is to find a balance between easy (not tracking) and hard (tracking) that you can stick with for the long term so you don't fall into the yo-yo trap. I lost 52 pounds in about 350 days five years ago, then gained 45 back over the next few years. I find keeping the weight off when I get to my goal to be much harder than losing it :-(. Now I am trying to lose that 45 pounds but do it in a way that I will be able to continue once I reach my goal weight.

For an Omelette I track the eggs, meat and butter/oil used to make it. The veggies are filler to me :-).

Good luck with your new journey!

Easiest way I found to do this was get kitchen scales and add your food then zero it and continue this process. I do this with dinner plates and weigh everything seperate.