how to add custom tag in Magento 2 using xml file

Don't worry about it because you can add div or any another tag what you need is it's easy using
xml file
Let's take 1 task as per example 

1 Step For above task we need to go first dir
this is for this task
app/design/frontend/Vicomage/scara_fashioncolor/Magento_Customer/layout

this is for any other task 
app/design/frontend/<Theme-dir>/<Module>/layout/layout

first open your file than after check code

now need to add this container tag in xml file

<container name="custom-content" as="custom-content" label="Page Custom
Content" htmlTag="div" htmlClass="custom-content">

<block your block /> 
</container>

 than after you can check it now added div here