This can be configured very easily.
When you Insert>TOC & Index>TOC, Index or Bibliography or, equivalently on an existing TOC when right-clicking and Edit Index, go to the Entries tab.
You can describe in Structure & Formatting what you want in the TOC entry lines. The chapter number (what comes from Tools>Chapter Numbering, i.e. the number and other decorators/separators) is coded as E#. Click on it and press Del.
Repeat for every level you want to customize.
To show the community your question has been answered, click the ✓ next to the correct answer, and “upvote” by clicking on the ^ arrow of any helpful answers. These are the mechanisms for communicating the quality of the Q&A on this site. Thanks!
In case you need clarification, edit your question (not an answer which is reserved for solutions) or comment the relevant answer.