Description:
LibO Writer has an "Insert -> Field" functionality that includes a "More fields" option which basically lets one include any kind of document property into a document, including custom properties.

LibO Impress also has an "Insert -> Field" functionality, however this is much more limited. There are only some basic fields listed corresponding to the most fundamental document properties and no "More fields" option. This basically prevents using the document custom properties as fields in presentations.

Conversely, this functionality would be quite useful. Think of slides where each slide needs to include a revision number. If there is a single master page the presentation depends on, the number can be put on the master page. However, if there are multiple master pages, updating the revision number means updating /all/ of them. Having the revision number in a single place in a custom variable would help a lot.

In principle being able to refer custom variables in a presentation would also help flows where documents are stored in vcs such as git. One could easily code an output filter replacing an output variable with a git id or tag, etc and have it referred inside the presentation.

Steps to Reproduce:
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Actual Results:  
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Expected Results:
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Reproducible: Always


User Profile Reset: No



Additional Info:
[Information automatically included from LibreOffice]
Locale: en-US
Module: PresentationDocument
[Information guessed from browser]
OS: Linux (All)
OS is 64bit: yes


User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Falkon/2.1.99 Chrome/56.0.2924.122 Safari/537.36