Here are my observations regarding your table:
This file was likely an Excel file at some point; it contains cell styles with corresponding names.
Large sections of the table (individual cells) have direct formatting applied.
Parts of the columns are formatted using the “Header” cell style (indicated by a black border).
In short, the formatting is a chaotic mix.
The table appears to be a monthly schedule that is quite compact and easy to read.
I see two ways to clean up the table.
In both cases, the direct formatting must first be removed.
Select the entire table (the active area) and press Ctrl+M, then:
- Create cell styles for the various cell requirements and assign them to the cells.
Cell Styles in Calc - The Document Foundation Wiki
- Select the entire table and apply an AutoFormat style.
In my example, I applied the “Financial” AutoFormat.
Of course, you can also create your own AutoFormat styles.
See: LibreOffice Bookshelf
138115 HB sample-file.ods (19,8 KB)