Another trivial technical tips I need to post for my own reference whenever I forgot about these seem-to-be-not-important things.
If you want to make a table with multirows like this in Lyx:

things won’t be as easy as creating tables with multicolumn. Lyx won’t allow you to right click and check the “multicolumn” option on the preference window.
Here’s how:
1. You have to insert these command in LATEX on the table like this:

this command
\multirow{4}{0.5cm}{the text goes here}
means that we set a multirow that consists of 4 rows with 0,5cm width and “the text goes here” as the text
2. Insert another scripts in the document’s preamble:

3. And there you go! A multirow table.
An official tutorial from Lyx here.
Thanks, great tip!