You can create User Defined Property in libreoffice writer. File – Properties – Custom Properties – Add Property – Set the type: Date) – Set the value.

To use this property goto Insert – Field – More Fields – DocInformation – Custom.

Settings > Digital Wellbeing and parental controls. Tap your preferred Focus Mode or create your own by selecting Add. Select Start to start using that Focus Mode.

If you use a font that the recipient is unlike to have, select Files > Proprties > Font > Embed fonts in the document before exporting to PDF. Note that embedding will vastly increase the file size if you you have a large number of fonts.

To open the Navigator, select View > Navigator, or press the F5 key, or select the Navigator in the sidebar.
On the simplest level, the Navigator lists all of a document’s objects, including outline levels – headings by default, other paragraph styles as well if you edit outline levels. Clicking a list item in the Navigator jumps to it in the editing window.

The settings for Tools > Options > Language Settings > Writing Aids > Options > Minimal number of characters for hyphenation. These settings are over-ridden by any formatting in the document itself.

The line divisions can be improved by running Tools > Language > Hyphenation as a final touch on the document. This tool not only works interactively, giving you more control, but also generally does a better job than the on-the-fly hyphenation, if run when the document is complete.

The Characters at line end and Characters at line begin fields can sometimes be manipulated to improve hyphenation by playing one off against the other. Working by itself, the Maximum consecutive hyphenated lines field can also make a difference. adjusting the settings on the Text Flow tab. The number of letters at the end and start of the line should be 1–4. The typographical convention is not to allow more than two lines in a row to end with a hyphen.

If you are using Libre office then template changer extension is very important.

https://extensions.libreoffice.org/en/extensions/show/template-changer

You can link the current document to a template or cut that link. Once the document is linked to a new template, all styles saved in that template will be available to be used. You can find the current template name by going to File - Properties.

you can select Edit > Find and Replace > Other Options > Paragraph styles to locate where a style is used in a document. "Attributes" and "Format" dialog box will help us find character styles.

In LibreOffice Calc, you can use function REGEX for e.g.
Begins with 'ph' will be =REGEX(A1,"^ph")
Ends in 'E' will be =REGEX(A1,"E$")

To use a custom paragraph style for a heading, choose Tools - Chapter Numbering, select the level and choose a style in Paragraph Style box.
You can also choose number 1,2,3 for each level if you need 1.1, 1.1.1 numbering for heading.

Turn Off Grid Lines
If you want to turn off grid lines in LO Calc:
Tools > Options > LibreOffice Calc > View > Visual Aids > Grid Lines > Hide

Get the distinct values in calc
1) Select the column (or the list of data) that you want to process
2) Data > More Filters > Standard Filter
3) From Options choose "No duplications".