Customization character indent before adding terms

I'm often have a list term with space, doublespace, dot character indent for children terms.
For example:

term1
  term1.1
  term1.2
term2
  term2.1
    term2.1.1

I propose to improve Batch add form to adding input element, which defined character indent.
By default this value set to '-'.
This feature add the ability to load custom terms list and removes a process of list preparing.