How to have full-width horizontal lines in Microsoft Word?

How can I have full-width horizontal lines inserted between the lines of a long text? I do not want to use Ctrl+U to add underline to the text because it does not add lines to the empty spaces. Also adding lines via the "Insert Shapes" menu seems not accurate and somehow hard to do for multiple lines. Is there any straight forward way to add full-width line between the lines of a text?

I also thought of simulating this with a table and pasting my text in the rows of a table with bottom borders. The problem with this method is that all of the text is inserted in the first row of the table, while I want each line of my text to be in a separate row.

The following can be used to add lines of different types. Try any of these:

In a new line, enter

1. Three hyphens i.e. --- and then press Enter button.

Result:

2. Three underscores i.e. ___ and then press Enter button.

Result:

3. Three equals to sign i.e. === and then press Enter button.

Result:

4. Three hashes i.e. ### and then press Enter button.

Result:

5. Three asterisks i.e. *** and then press Enter button.

Result:

6. Three tildes i.e. ~~~ and then press Enter button.

Result:

This is fairly simple:

1) From the ribbon, select Insert - Shapes - Line
2) Draw a line across the screen where you want it
3) Right-click on the line and select More Layout Options
4) Select the Text Wrapping tab
5) Select In Line With Text

You will now have a line across the document that will stay in place relative to the text around it.

You state in the question that Insert Shapes is hard for multiple lines. Not so if you select the In Line With Text option.
Note that the default is In Front of Text which is probably where you are finding the difficulty. This option does not move the line with the text as it is edited.