It is possible to insert a business component variable in a form as any other variable, through the Insert / Variable menu or the associated shortcut or through the toolbox.
The following dialog appears and you are available to delete the properties which you don't want to show in the form:
If the business component variable has nested levels (as the previous image shows), they will be inserted in grids.
For example, when the &invoice business component variable is inserted in a web panel form, it looks like this:
As the variables in web panels are editable by default, all the &invoice properties are editable.
If you want to allow the user entering an invoice id value, then pressing a button and loading all the invoice data, look the following solution:
Besides, if you set the AllowSelection grid property = True (to allow the user selecting a line), you can use the CurrentItem property, for example like this: