Try adding the following macro to the 'ThisDocument' code module of your document or its template:
Code:
Private Sub InsertFootnoteNow()
Dim Rng As Range
Application.Dialogs(wdDialogInsertFootnote).Execute
Set Rng = Selection.Range
With Rng
.Start = .Start - 1
.Text = vbTab
.Move wdParagraph, 1
.Select
End With
End Sub
For PC macro installation & usage instructions, see:
http://www.gmayor.com/installing_macro.htm
For Mac macro installation & usage instructions, see:
https://wordmvp.com/Mac/InstallMacro.html
You can adjust the effective size of the tab by modifying the Footnote Text Style and adding a left tab-stop to it; you could also apply a hanging indent, etc.