For control of layout of an entry in a Table of Contents - is it possible to include a tab character in an index entry (added via menu: insert > Table of Contents and Index > Index Entry…). the tab key advances to the next field in the dialog.
Right click the TOC and select Edit Table of Contents, you can add a tab stop in the dialogue in the Entries tab. It will apply to all entries at that level, see Entries (table of contents)
.
Note that you can manually edit the TOC for a single but it will be overwritten on the next update of TOC.
.
If this is not what you meant, maybe you could give a more complete description of what your goal is for the TOC and maybe a small sample